I know this is really old, but I just want to say I think Sita was gay. I believe she did try to make her marriage work due to societal norms, but basically right from the start she realized she would not get what she desired from her husband. That said, I still think Sita was gay. Right before she kisses Radha for the first time she is crying and Radha thinks she is crying because of her husband but Sita says "It's not that" and then kisses her. That makes me think she is gay. Also there was a scene where Sita's husband was going to have sex with her, but she turned him down so Sita could have had sex with her husband but didn't want to.
I think it's harder to define Radha. She has suffered years of a loveless marriage and now here is someone who loves her and desires her. Whether or not Radha was gay, she did fall in love with Sita.
I think it's really hard to define homosexuality in a film like this because the society portrayed doesn't even acknowledge the idea. Both women have probably gone about their life fulfilling the basic duties of women. They marry or were arranged a marriage and are then expected to have children. The idea of being attracted to a woman probably doesn't even cross their mind. I mean Sita was in an arranged marriage because that is just how things are. She didn't marry because she was attracted to her husband or had feelings for him. So I think in a context like this it's really hard to place such labels.
I will say I do not think they were just experimenting. They had a general pull towards each other or else I doubt the relationship would have gotten as far as it did. It also seemed like Radha acknowledged that Sita was the only one she had had such strong desires for.
Of course Sita was gay. Radha I believe was also gay, but she was at least bisexual. There was genuine love and attraction between the two.