Is it normal for a female to change when talking to her bf?

I was with a female friend the other night who is a single parent and very competent. Anyhow, she's been getting grief from an ex bf and her attitude was 'stuff him'. However, when her current bf rang, I heard her change her tone as if she was all upset over her ex's phone calls. She wasn't even even answering them! So I was like wtf is she playing at? Why is she pretending to be a weak female? What is she trying to achieve, except get her current bf all worked up against her ex?

I am really confused as to how she can be talking so normally one minute and then half pretending to cry the next to her bf?

Is this normal? Please comment if you understand her motives because I am completely baffled. Thank you.