I need you love advice please

I need your guys advice i have been currently talking to a co-worker of mine at work we have become friends since. The thing is I really like her and she likes me but she has a boyfriend which sucks obviously. I never thought I could like someone knowing they were in a relationship but it happened. She tells me she really likes but she has been with the guy for about 2 years and says her heart belongs to him. You see her relationship is not that perfect they occasionall have fights and stuff I guess just like any other ralationship but I treat her completely the opposite of what he treats her and thats what she likes about me. And knowing that they are having problems was the reason I actually began getting closer to her we txt message we were talking on the phone but she got caught so that has stopped. So we only talk at work. But just recently in the last week or so we started hugging each other and kissing each other on the cheek. Now just yesterday we actually kissed on the mouth and made out briefly but it was nice. Today was even better cause I got to spend more time and all we did was nothing but kiss it was the best. But it just sucks that she is still with him. Im getting to the point were I can say that im starting to love her. I know what me and her are doing is wrong but sometimes you just got to do what u have to do and not hold back. I need your guys advice wether is positive or negative will be appreciated. I just would like to win her over but thats the hard part since she claims to be in love with him but at the same time if you are really in love with someone you won't cheat on them now would you?