The 38-year-old actress stripped off for the steamy romp as character Elyse, who strikes up a saucy romance with Lena’s alter ego Becks.
In one sizzling scene, topless Mena and Lena lock lips as they lie in bed together with nothing but a duvet to protect their modesty.
The women convincingly play a loved-up couple as they tenderly stroke each others hair while sharing a tender kiss.
Another snap showed a naked Mena arched on the bed with her cleavage on full display as Lena stood behind her.
Clearly surprised by a sudden encounter the women gasp in horror as they appear to be caught in the act.
Becks follows the story of a Brooklyn musician, who after breaking up with her girlfriend is forced to move back in with her Midwestern mother.
In her hometown, she scrambles to make ends meet and has to play music for tip money in an old friend’s bar.
However, she embarks on an unexpected relationship with Elyse and the pair soon share a few steamy romps.
The drama is based on the life of singer-songwriter Alyssa Robbins and stars Christine Lahti, Hayley Kiyoko, Dan Fogler, Wally Dunn and Isabelle Farrell amongst others.
In the tantalising trailer, Becks is forced to leave town after she finds out her girlfriend has been cheating on her.
Broke and back home living with her mum a friend of hers offers to help out by letting her perform at his bar.
Eventually, she meets Elyse, a suburban housewife, and they start having a secret relationship.
Mena, who shot to fame in movies such as American Beauty and American Pie, recently discussed how her role in the film differed to ones she has played before.
She told Build: “Sometimes you can work on a project and it can be so specific but to me, on this project [Becks] there was just so much freedom involved.
“We were really able to create and we didn’t have to worry about any of that. There was just this realness to it and that’s what I’ve always preferred in a way.”
This summer, Mena will make her debut in the new drama series American Woman, which is based on the life of reality star Kyle Richards.