To make her your girlfriend even when when she currently has a boyfriend, you have to be patient. You are not going to speed up the process by pressuring her to break up with her boyfriend. In fact, doing so can be detrimental to you efforts.
Even if she has decided to leave her boyfriend, it can take anywhere between 1 week to 4 weeks to finally truly end things with him. So remember to step back and just let her do her thing. There can be many reasons why this can take some time.
- They are living together. She needs time to find another place and move out
- Emotional blackmail. The boyfriend could be using their past happiness to blackmail her
- She needs time to get over the fact that things are over. This is just a phase
- She need to get support from her friends
- She wants some time to see whether you are going to stay around
Continue to be the guy she fell in love in the first place when she had a boyfriend. Play to your strengths and note down the qualities that she like about you. Casually display these qualities consistently whenever the 2 of you meet up.