Is it ever a good idea to try to steal a girl from her BF?

I had a big crush on this girl who gave me mixed signals. She has a BF in another city (not lying), but flirted with me in the beginning with this innocent way to talking. I helped her with some career advice and she asked me to dinner/drinks. At dinner, she flirted/suggested that I should even go after girls who have BFs. But whenever I reciprocated with the flirting, she backed off, but we basically drank all night in her apartment. She has a roomy, so nothing happened. Then, she gets me a postcard when she was on vacation. I asked her to dinner, but she ignored my request, only to ask me two weeks later. I thought she was a playing me, so I refused. That week, at a party, she was visibly jealous when I was dancing with other girls. After 5 weeks of silent treatment, at a party, we got real sensual on the dance floor. She said "I'd like to get to know you", but again gave mixed signals the next day by saying "I'm a ball of ual tension". I find her very attractive. What would u do?