Martha was NOT lesbian

1). At the time that she claimed to have lesbian feelings towards Karen, Martha was extremely distraught, so she was not reliable; her words at face value are highly questionable at this time.

2). The entire movie showed that the lie ruined their lives, and there was nothing they could do to escape the lie: their alleged lesbianism had already been heavily publicized, and they lost their lawsuits. Martha's claim that she loved Karen may thus be interpreted as a sign of her frustration. It's as if she is saying, "I can't get away from this lie no matter what; I may as well say that it's true"

3). If Martha were really lesbian, then the little girl's lie / rumor had a positive effect: the lie / rumor brought out her true feelings. But this interpretation destroys the essence of the movie, which aims to criticize the effect of lies / rumors. Thus, the idea that Martha was really lesbian doesn't accord with movie's theme.

4). If Martha were really lesbian, then that is extremely coincidental. The little girl just happened to spread a lie / rumor that was actually true?

All things considered, the best conclusion is that Martha wasn't really lesbian. Martha just claimed lesbianism out of frustration