Question: how to know if your ex girlfriend is talking to someone else?
Answer: Ignore you. The first sign is ignored you. ... 
Avoid you. You and your ex-are classmates, but a few days after breaking up with you she starts to avoid you. ... 
Hard to contact her. ... 
Delete your photos on social media. ... 
Returns items previously given. ... 
Forget the important moments with you. ... 
Ordinary behavior. ... 
Assume you are just friends.