Does she want my man?

My husband recently made some new friends. He got into the LPN program at the trade school and he made friends with a guy and a girl. My husband doesn't really have a lot of friends. He has autism and is socially awkward. I've met the girl and she's super pretty and perfect in every way. I guess I shouldn't be threatened because she's supposedly a lesbian. She just doesn't look like a lesbian. And I know gay people come in all different shapes and sizes. To me she just isn't giving lesbian. Anyway she came by to study and saw a picture of my husband's sister and said she was hot. My husband said his sister is bisexual and they started talking his sister and he took a picture of her to send to his sister for permission to give out her number and his sister allowed him to. I know sounds innocent. But his sister is also his TWIN sister. My husband and his sister look exactly alike. If she's attracted to his sister doesn't that mean on some level she's attracted to him?