The 36-year-old said she is 'so in love with' Busy, 37, after they walked the red carpet together at a special screening for her latest film, Manchester by the Sea

Busy flew to New York from her home in Los Angeles to support her fellow actor and longtime friend at the screening

The two ladies have enjoyed a time-tested friendship dating all the way back to 2001, when Busy joined Michelle on the cast of Dawson's Creek

Michelle Williams' friendship with Busy Philipps has not only stood the test of time, but the actress insists that her best friend is the true love of her life.

The 36-year-old mother-of-one couldn't help but gush about her pal on Sunday night at a special screening for her latest film, Manchester by the Sea, at the Crosby Street Hotel in New York City.

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'I’m so in love with her,' Michelle told People. 'She’s proof that the love of your life does not have to be a man! That’s the love of my life right there.'

Gal pals: Busy Philipps (R) posed with fellow actor and long-time friend Michelle Williams (L) Sunday night at a special screening for Manchester By The Sea in New York City

Old friends: After the event, Busy took to Instagram to share a photo of them at the screening, along with a picture of them on a night out in 2001

Strike a pose: Busy pointed out that she and Michelle almost always stand on the same side of each other when they attend events together

Busy, 37, frequently walks the red carpet with Michelle, and for this particular occasion the mother-of-two flew to New York from her home in Los Angeles to support her fellow actor and longtime friend at the screening.

The event was sponsored by Louis Vuitton, and as such, the two beauties really brought their A game in the fashion department.

Busy, whose legal name is Elizabeth Jean Philipps, wore an all-black top with long sleeves, a high neckline and lace embellishments. She paired the top with black leggings and black combat boots, and accessorized with a silver and black pendant and colorful clutch.

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Side by side: The two attended the 22nd Critics' Choice Awards together, held in Santa Monica on December 11, where Michelle was nominated for the category of Best Supporting Actress

Bathroom selfies: Busy happily snapped a photo when the two went to the restroom together

Michelle shimmered upon her arrival in a dainty black slip dress covered in a sheer overlay that showcased sparkling, silver accents. She wore open-toed, ankle strap black heels and carried a simple black clutch.

Both actors wore rosy makeup with a pink lip, with hair chic and straight for the event.

The two ladies have enjoyed a time-tested friendship dating all the way back to 2001, when Busy joined Michelle on the cast of Dawson's Creek for seasons five and six.

While reminiscing about their friendship, Busy took to Instagram on Monday night to share a photo of them from the screening along with a picture of them from 2001.

'2001/2016,' she wrote. 'I love that we almost always stand on the same side of each other. Also, can I just say-we aren't at a costume party in 2001.

As close as can be: Michelle gave Busy a kiss on the cheek after someone accidentally spilled a plate of mini crab cakes in her hair

'That's legit how we were dressed for a regular night out. I guess I really was my character from Cougartown? And thank God my eyebrows grew back,' she joked of their outfits.

Busy also accompanied her pal, Michelle, to the 22nd Critics' Choice Awards, held in Santa Monica on December 11, where the latter star was nominated for the category of Best Supporting Actress for her role as Randi in Manchester By The Sea.

Michelle has an 11-year-old old daughter, Matilda, with the late actor Heath Ledger, and she admitted during a recent interview with Porter magazine that she didn't expect to be 36 and still dating as a single mom.

'I know a handful of women in similar positions [to me], it’s kind of like a club,' she said. 'It’s a s****y club and we don’t want any new members… and all of the current members are exhausted. But man, oh man, it’s lifesaving to have [them].

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'My friend Busy [Phillips] and her husband Marc [Silverstein] said, "Michelle, you’re in like a blackout zone, everybody is now partnered up and you have to wait for people to start getting divorced." Oh my f*****g God…'