my (23F) partner (25F) of two years recently told me she’s been desiring sex with men and she’s interested in opening our relationship up. i’m a lesbian and she’s pansexual. i’ve always been monogamous so this idea is quite jarring to me. she’s assured me she still loves me and is attracted to me. she also keeps telling me there’s nothing to worry about because she thinks of sex with others as an extension of masturbation and it would just be a way to get off. our sex life has not been great for at least a year. she already has a close guy friend in mind that she’s had casual sex with a couple times before we met. i’m feeling jealous and i’m scared of her developing feelings for someone else even though she is adamant that this would never happen. i keep telling her that no one can predict or control their feelings but she doesn’t see it my way. should i at least let her do it a couple of times and see how i feel before totally rejecting the idea? am i overreacting? i’m feeling really confused and sad and i don’t know what to do