overreacting?

so my fiance wants me to take modeling photos of her in her pink underwear and sometimes us both like naked but like her leg is over my area and she is on my chest not revealing anything kinda. she wants me to post them on fb and Instagram etc but I told her how i feel that it will make me jealous and that she will get guys hitting on her maybe. she says it will make her feel happy and pretty and that i can show off my fiance and show what I have and they can't have. am I over thinking this? am I letting my insecurity get the best of me?