Should I do it or not ?

Hello everyone I have been in a relationship with my gf from past 9 months and she told me about her ex's before like hanging out with them or kissing and it was really distressing for me I was in severe depression and anxious all the time feeling really jealous eventually it got better with time but If I still try to remember those things it just fucks up my mind. Recently I found that she had used facebook too and forgot her password but I can reset it somehow and I really want to check her Facebook to find out what was hidden from me and what was told to me my jealousy has been eating me from inside I asked her should I open up the Facebook she told me that she used that account long time ago so she also doesn't even know what is inside the account and told me to not to check it because it can mess up my mind again but I really want to go through that account what should I do please help me guys ?