It's no secret that many of the show's storylines are based on Dunham's personal experiences. And on that note, Dunham assures us that just because the girls are showing signs of maturing, doesn't mean they are in for any less of the awkward and embarrassing misfortunes that have become a trademark of the show.
"There's plenty of humiliation to be found in my life now and I just kind of pass it on to my characters," the 28-year-old New Yorker says. "That's why we've really taken it up a notch with Marnie singing embarrassing songs in public places.
"I always thought before I had success in this field, that success and acclaim are like the great magical equalisers that erase all the problems from your life. Unfortunately I have found that that is not the case. I still have plenty of pain and embarrassment to use as inspiration."
The success Dunham is talking about isn't just from the show - although as well as taking out the Golden Globe for Best Comedy Series in 2013, Dunham has earned her own Golden Globe for Lead Actress and recognition from the Directors Guild of America for Outstanding Achievement.
Over the past two years Dunham has become a pop culture star and a feminist icon.
She has made herself known as a loud voice on issues such as gay rights and sexual harassment and last year her collection of essays Not that Kind of Girl made the New York Times Best Seller List. The icing on the cake is her growing reputation as friend and inspiration to the belles of Hollywood (most notably, Taylor Swift has repeatedly credited Dunham with helping her understand what it means to be a feminist).
Dunham takes it all in her stride.
"I'm really just trying to share my experience of being a female and hoping that it makes other women feel less alone."
In season one of Girls, when petitioning her parents not to cut off her financial support, Hannah proclaims that she may be the voice of her generation. That line has since become extrapolated to stand for Dunham's views on her own work.
Dunham laughs at the idea, pointing out that her character was on opium when she made that comment.
Nonetheless, Dunham and her characters have been consistently criticised as symbols for all that is wrong with today's youth: self-involved, entitled and aimless.
"I feel like a big way that millennials have been talked about is as very apathetic, as people who don't care about politics, who just wanted to sit out there on their twitter and blog pictures of their snacks."
But she says that's not the case at all and refers to recent protests about police brutality in the United States as an example. Dunham says the reaction to her work is a sign of how threatening millennials are to the status quo.
"To be completely honest, I think that old white men find young women speaking very threatening and that's just sort of a fact of the time that we live in right now."
It's not far-fetched to say that the criticism of Dunham's work is a classic example of generational differences; after all it's almost a requirement in reaching a certain age to bemoan "kids these days". And Dunham admits that even she is feeling more and more removed from her character, who is now a few years younger than her.
But the show can't freeze time forever. So when will the girls become women?
"I think about that all the time. We're going to end up in a position where we're all going to be 35 and pregnant and calling the show Girls is going to start to feel really ironic," laughs Dunham.
"You know, it's funny I think, in some way, girls always feel like girls no matter what age we reach but I think my goal with the span of the show is to see the characters from a place of real youth to a place where they have actually matured and made real changes in their lives. That's what I want to see."
TV profile
Who: Lena Dunham
What: Girls season 4
Where and when: SoHo, tomorrow night 8.30pm.
