Why women fall in love with other women?

There is no concrete answer, unfortunately, it's just one of those things. The same could be asked about men falling in love with men, it's down to preference and taste. Some women may be straight and then gay the next! same for guys.

But no matter what sexual preference someone has, they should be accepted, they are still human and deserve respect. I do not see a problem with straight guys / girls mingling with otherwise gay guys / girls, providing they respect your sexuality and do not try it on with you, heh.

Hope that answers your question.