Allison Williams' freshly-manicured forefinger and thumb are currently teasing out a loose goose feather that's poking out of the couch, her diamond eternity band glistening as her nails pincer around the innards of the hotel room's upholstery.

'Acknowledging there's a ceiling is very important,' she admits, as we ironically discuss the impossible strive for perfection.

With a circumspect look at her, at least, it doesn't seem like Allison Williams has, herself, hit any ceilings on her way to 'perfect.'

The 28-year-old actress is outwardly quite flawless and seems to have led something of a charmed life up to this point.

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After all, the Connecticut-born star is the daughter of notable NBC anchorman Brian Williams, a graduate of Yale University and she caught the attention of renowned Hollywood producer, Judd Apatow, after he watched a widely-praised YouTube video of the, then 22-year-old, singing a mashup of the Mad Men theme tune in 2010.

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Months later, Williams found herself cast in HBO's Emmy-Award winning show Girls, and has since nabbed the title role on NBC's live television presentation of the musical Peter Pan Live! and married the co-founder of comedy website CollegeHumor, Ricky Van Veen – a wedding officiated by Oscar-winning actor Tom Hanks. Of course.

Couple all of that with the fact she's seriously glamourous, wore a couture Oscar de la Renta gown for her big day and counts her Girls co-stars and singer Katy Perry among her closest friends, now we're thinking about it, Williams might just be the sheer embodiment of perfection.

Well, that is until you come face-to-face with her.

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I meet Allison at a London hotel, days before the international women's march and amid the press tour for the sixth and finale season of Girls – the show that has been her life for the best part of six years.

Picking up where the last series left off – *SPOILER ALERT* which saw Hannah tell an audience of strangers about how her best friend is now sleeping with her ex-boyfriend, perfectionist Marnie fall for coffee shop manager Ray, Shoshanna take over the marketing work, and Jessa and Adam come to terms with their new romance – it's hard to believe the sixth season could be set for more drama, soul-searching and Hannah talking about her need to be the 'voice of a generation'.

Of course, in true Girls fashion, it fails to disappoint – much like Williams.

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Perched on a chair opposite the actress, I can't help feel the need to remind myself I'm not, in fact, chatting with a best friend.

Throughout the interview, Allison peppers our conversation with profanities, tucks her feet up beneath her knees on the sofa like a teenager to get comfortable, and repeatedly tugs on the hem of her grey midi-wool dress, wrapping it over her bare feet.

'Sorry about those, they were killing me,' she jokes mid-conversation, noticing my gaze drifting towards her abandoned high heels that lie haphazardly under the coffee table.

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If you think Allison Williams is perfect, you're be pleasantly mistaken. While she might have the dream job, be married to a multi-millionaire, boast a famous friendship group and own one of the most covetable wardrobes in showbusiness, she's also a pretty average twenty-something and, importantly, that's also how she sees herself.

With the goose feather finally exumed, here's what Allison told ELLE UK about what's in store for our favorite female foursome in the final season of Girls.

Girls was certainly a groundbreaking show when it aired in 2012. How do you think it has influenced a generation of millennial women?

Allison: I hope they've learned from our mistakes. Sometimes you have to make the same mistake a couple of times before it actually gets through – Marnie is case in point.

Girls has shown that not everything has to be cutesy or set up; your apartment and friends don't have to be perfect, you don't have to be perfect and your sex doesn't have to be unawkward and seamless. The show presents what real life looks like. We're all doing our best, but mostly we're failing.

When you watch the show, you get to take comfort in our tiny failures. With any luck, the non-aspirational aspects from [Girls] will have made people feel comfortable, no matter what their status quo.

Having worked on 'Girls,' what have you learned about beauty and women?

Allison: As a reaction to the relief people feel from Lena opening the door to unconventional, non-perfect bodies, I've learned how much people feel the need to look like a certain type of person.

Since no one has the perfect body, the show was made to show real bodies doing real things. We haven't set an impossible standard people must hold themselves to.

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However, this has meant that what guys have previously looked for from their TV shows – the more scintillating, almost borderline pornographic relief – hasn't happened with Girls, which made a lot of them angry. But, for women, it was a relief.

We're all doing our best, but mostly we're failing

I hope Girls has been incredibly soothing and helpful for viewers, showing completely different body types. Even between the four of us – Lena, Zosia, Jemima and I – none of us can wear the same clothes.

Our photoshoots are hysterical because you walk in and immediately know who's rack is who's, depending on the prints, proportions, designers and silhouettes. None of us are perfect or look the same moment to moment.

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You say that but your character, Marnie, is the ultimate perfectionist. What would you say to women who feel crippled by the ideals of perfection?

Allison: It's funny because when I was little, I use to make a list of things I should do when I get home from school. They included tasks such as 'practice piano for at least one hour', 'have a little snack', 'feed Lucy' and 'do your homework best as can be'. The 'best as can be' part is something I knew then, but briefly forgot.

Later in life, that part has come back to me and helped me realise that perfect is irrelevant – strike it from your mind because it's not even worth thinking about. Acknowledging there's a ceiling is very important.

The 'can be' means both what you are capable of doing to something, and what it can be. There's an inherent limit to everything.

A lot of women are feeling disillusioned with politics and the state of the world. What would you say to these women?

Allison: A lot of women are going to be marching on Saturday, but I think there's always an opportunity to accept who we are in the small, daily, radical things we do just by being women in the world.

[We need to reject] the idea we are in any way inferior or less deserving than our than our male counterparts. It isn't always about putting them down to elevate us, it's about making sure that we're on the same playing field.

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The international women's marches will be a day of catharsis and healing. It's not an anti anything necessarily, more an assertion of self and an opportunity to feel the support that really only comes from a big gathering of people who feel the same way. It's about solidarity.

How has Girls been able to successful straddle the concept of creating flawed yet likeable characters?

Allison: I give all that credit to the writers. Lena, in particular, captured a realism and familiarity for the characters. I don't know anyone that's simply a heroine or villain – it's so much more complicated than that – and the women in Girls are emblematic of this.

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For example, Marnie makes maddening choices that drives me crazy because I just want to correct her wrongs or soften the blow in some way.

There's always an opportunity to accept who we are in the small, daily, radical things we do just by being women in the world

Even when I know it's a bad idea to walk into Charlie's office and sing Stronger, Marnie doesn't and she thinks it's the right thing to do, which weirdly gets her what she wants. She has balls I can't imagine having. I know the way her mind works and it's just a couple shades too selfish. I think she'll grow out of it.

How does it feel now Girls is over?

Allison: It's strange. It's nice to be able to talk it through – it's helping me process it. You finish wrapping and that's emotional because you're done playing someone for good. Then you promote the show and it comes out, which is moving because it's the beginning of the end.

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And, then the finale ends and that's really the end. Then there's award season which is usually the last go-around of everyone parading around as a cast and then it's really over.

What do you think Marnie would be doing in 2030?

Allison: I can see her going into a very modern relationship like an incredibly devoted marriage to someone who is gay – it's the only relationship I can see working for her.

They would both be allowed to do whatever they want to do for their sexual needs, they'd feel nourished by their relationship and would be completely devoted to each other.

They'd get everything they need but from a couple of different sources, eschewing the Swiss army knife idea that you need to find everything in one person.

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I hope she'll doing something that puts her intelligence first before anything else. I think she's smart but isn't focused on that yet and that's okay, she'll come into it eventually. Marnie's got ideas, she's a smart person.

Girls Season 6 premieres exclusively on NOW TV and Sky Atlantic on 13 February at 10pm, or binge on the complete S1-5 Box Set now.