I thought she was a lesbian until I saw the man.
Is she dating this man?
She was being flirtatious with the guy, making out with him.
Someone's sexuality can be a surprise if you have already made assumptions.  For all either of us know, she could be bisexual.
Eh, I still think it's gross.
This young woman that you are talking about has found someone that she is attracted to, so we shouldn't judge her for that.  There is nothing gross about other people's affection, though sometimes people do tend to go overboard in public.  Let's just both be happy for the couple.