been there, done that.
the reason she does not trust you, is becoz she does not trust herself, her "friends" might be more than that, and since she knows her behavior is inappropriate, she probably thinks ur behavior would be inapropriate if you had female friends.
bottom line she does not trust you because she herself knows she cant be trusted.
Disclaimer: not saying your wife is a cheater, but ive seen this pattern before first hand.