Jemima Kirke, one of the stars of HBO's Girls, may shudder to think of herself as an actress, but on season five, she really came into her own as Jessa, the often disillusioned gal pal who gained control of her addictions and found a new confidence in herself. It's been quite the journey for Kirke, who considers herself an artist first and told creator and best friend Lena Dunham when she first joined the series to keep her limited to a few scenes -- to make her "background information."

"In the beginning, it was just wasn't my vocation," Kirke tells ET about her seemingly accidental career as an actress. Prior to Girls, she appeared in Dunham's Tiny Furniture. "I was uncomfortable about it, just in terms of my identity. Then as I got to do it more and got really into the actual -- and I hate saying this word -- the craft of it, I was like, 'You know what? F**k this. It's just as good as painting.'"

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"I think [Lena] saw a change in me, in my desire to do this, and that's when a more dynamic story came into my arc," Kirke says. "It's been an ongoing conversation for us. We're very close and we talk about it all the time, so I'm always expressing how I'm feeling about it every day. So, she just witnessed the evolution I suppose." Of course, audiences know that season five challenged Kirke with her biggest storyline yet as Jessa started dating Adam (Adam Driver), Hannah's (Dunham) ex-boyfriend, and the two became temporary parents to Adam's niece.

The decision to pair them up, Kirke reveals, wasn't an easy one. At times, Dunham was sure about it, first planting the seed in season four, but then changed her mind. "She eventually came around to it on her own, but I didn't say anything because it's not my place," Kirke says, adding that she was excited about the opportunity to work more with Driver while any fears about how their relationship panned out was in the hands of the writers. "I have fears like that all the time. But I'm not a writer and I'm not in the writers' room. I've learned to trust that they know what they're doing."

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The result was a legitimate romance that blossomed between two characters who have always had great chemistry together in the few scenes they shared in earlier seasons. While Adam dived in headfirst, Jessa was far more conflicted, blaming him for what she believed to be a divide between her and Hannah. "She's blaming him the whole time. Obviously, she's accountable," Kirke says of Jessa and finding that balance between her hesitancy and vulnerability onscreen. "I figured it out, but it was a challenge to straddle that."

The storyline eventually culminated with a knockdown fight with Jessa telling Adam that she can never forgive him for splintering her friendship with Hannah. While the scene left dire implications for the two, Kirke admits that she had a great time filming it. "Oh my god, it was the most fun thing I've ever done," she says. "I got to throw a bookshelf. I got to be picked up by Adam Driver like I weighed two pounds."

What is abundantly clear after talking to Kirke, though, is that she's no longer content with being a background player. "It was probably the first season where I had people actually coming up to me and commenting on the storyline," she says of fans' reactions. "It was very much appreciated. Not that I don't love just being in the mix, but it was nice to hear, 'Your stuff is great.'"

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