Chicky troubles

Ok i've known this chick for a while. We work at the same place and chat and text alot. She has given me nudey pics before and i like her alot and i think she likes me. BUT when i asked her out about 3 months ago she responded with "sorry i have a boyfreind at the moment". There was no mention that she dosent like me and we still talk and flirt alot. now her and the boyfreind have been on and off since then and recently there have been more fights than before. Im pritty shure that it wont last and they will break up but i dont know if they do cus we dont talk about him and on facebook she is married to one of her besties. im just wondering how i should go about this