Most Helpful Girl
Only she knows if it's a rebound or not and it's best not communicate at all. Don't respond if she txts you. Let her relationsgip runs its course and try to focus on feeling better instead of your exs new bf.
Most Helpful Guy
If its only been over for 4 weeks then its most likely a rebound. I don't care what the research says about rebounds being good for you they're not they just stink of desperation of not wanting to be alone. If she contacts you tell her to do one you don't need people like that who will jump into another relationship straight after. Speaking from experience my ex sounds exactly like yours loads of insecurities and hates being alone and needing someone there for her all the time.