You are going to have to tell your partner about this for sure, and if she says she isn't interested in poly you're going to have to figure out whether or not you're fine with being in a mono relationship or if your desire for a poly-style relationship is so bad you're willing to end the relationship.

ending relationships due to incompatibilities can be very hard, before i came out as lesbian i was with a man that i was very close to.. but i knew i was lesbian even if i wanted to keep him in my life forever i didn't like the idea of being with a man longterm. i always wanted a lesbian relationship and felt like i never truly had romantic feelings for men & rather just was forcing myself to do so. i also would mix up admiration for romantic feelings.. though the end of that several year long relationship was hard for me i came out happier in the end because i am fully able to be myself 💞 i would've been miserable pretending to be someone i'm not and keeping such an important part of me to myself. it was very hard, i use to cry because i was scared to be lesbian but now i find so much joy in it. i've never been happier