It may be best to distance yourself from her.
Being that she only broke up with her boyfriend three weeks ago and has told you that she needs time, there is a good chance that she is still experiencing emotional repercussions from that breakup.
Even though she told you that she will not go back to her ex, that doesn’t necessarily guarantee that she won’t.
If he were to come back into her life right now and beg her to give their relationship another chance, given her current emotional turmoil, she just might do that.
It is best that you don’t keep going out with her and accepting her invites to parties.
If you get too involved, you may end up developing feelings for her that she will be unable to reciprocate due to the possibility that she still cares about her ex boyfriend.
As of now, it is okay to be friendly when you see her or happen to be in the same social environment as she is.
However, you should stop interacting with her on a one-on-one basis.
She can give you all the signals of interest in the world but if she has told you that she needs time, she hasn’t gotten over the breakup.
If you don’t take a step back, you could easily become a rebound.
A rebound is often used for a certain period of time and then discarded when they have served their purpose.
That is not a good place to be.