How do you know when your wife is attracted to woman?

Body language.

If a girl is into you, her eyebrows will raise for an instant. it'll happen for less than a second and you have to be very sly to notice it.

If a girl is into you, she'll toy with her hair. She may start to move a ring on and off her finger (this subconsciously resembles a phallus and a vagina), or anything that looks similar to that movement.

If a girl is into you, she'll start to mirror your movements.

If she starts to bite her lips, bat her lashes, lick her lips, ect, those are all signs she's into you as well.

Exposing her wrists and her neck are also a very good indication.

Good luck