How to win her over?

yes i'm gay, please no -phoebic comments. so i'm in love with this girl i have been for a long time i mean shes the reason i found out i was gay. well she has a gf, this girl in my cl-- k i'll call the girl jess and her gf liz. well, theyve been going out like 4 weeks and liz is just really a jealous person, and that bothers jess. and liz is mean to jess, always telling her what to do and yelling at her. well the other day, me and jess were talking and...idk how it happened, we kissed. and i KNOW how wrong that is since shes taken, i feel horrible, even tho truthfully it was the best moment of my life. so her gf hates me now. she didnt dump jess, apparantly shes giving her a second chance. jess meanwhile says that she likes me so much and she is ALWAYS staring at me and making excuses to get close to me. and i love her, but idk what to do, if she likes me that much she should dump liz. i want to be with her, and i kno if i do sumthing then she will want me 2 but idk what i CAN