Marla and Trish's argument about sex is brief, but is not about Andy. It's Trish being angry that Marla has invaded her privacy, and Marla being angry that she is not allowed to have sex, unlike her mother.
See Also
In honor of women's history month, here are some of the Editorial Board's favorite movies that pass the Bechdel Test - The AggieKIDS FILMS THAT PASS THE BECHDEL TESTDoes Shakespeare pass the Bechdel Test?They argue again about it later, and Marla's desire to get on birth control. That does not include or involve a man at all.
Then they discuss early pregnancy and how Trish was also a young mother, and how her older sister was a "mistaken pregnancy".
The movie passes all three tests.
