<human>: Condense the text into a few key points

Been with girl for around 6 months, we had a shaky start as she wanted to keep her exboyfriend as a friend, didnt want to hurt him so we had to start the relationship really slowly.

recently her exboyfriend told her that he has found a new girl, she says she is shocked but i react by thinking she must still be attached. Why would she care if he gets a new girlfriend, the way she has been acting since feels like the boyfriend has broken up with her. 

dont know what to do, i have asked if she is still attached and she gets really defensive and aggressive telling me i have nothing to worry about. i just cant understand why she would care at all that this guy has got a new girl. She also says it happened so soon that it made her feel shocked.

She says all her friends had the same reaction but i still feel she is attached to this guy, she has been extremely strict and reformative with our current relationship aswell since hearing this news. Also trying to book a trip to do something like she is trying to get away from it. 

can i get a girls perspective on this and tell me how i should react. Also how can i support her through this if i can
<bot>: Girlfriend left ex for me but is 'shocked' after hearing her ex has found a new girl after 6 months. (they were together 4 years but for 2 of those we had been talking)