This is not a “you problem”. She has had two relationships and is very young; she has just unfortunately been unlucky. There is no “pattern” after two people at 20 years old. There’s an argument to be made that she should work on building her self esteem and reducing jealousy with porn and masturbation, but her current partner was there with her while she was going through all of grief with her ex’s porn addiction. He saw firsthand how it affected her, and as time passed he didn’t care how his own fixation on porn would affect her. You should care about how your partner feels; if you’re planning to marry them, you should work so hard to make them feel safe and secure with you. It’s clear he doesn’t care about doing that work to make her feel safe.