Girlfriend met with her ex without me knowing

Hello everyone,

I am writing this thread because I caught my girlfriend texting to her ex.

She was showing me a chat on WhatsApp when I saw his name. Obviously I couldn't let it go after she had told me how much he hurt her, how he left her to go have fun with more girls to get more experience, etc...

So I opened her phone, doing the only thing I hate the most in this world (because it's privacy invasion and my parents tend to do that to me when I was younger so I hated doing this to her and I felt pretty bad and told her this afterwards).

So, long story short, I saw that she had been chatting with him for the past 2 weeks and how he was telling her he had changed and that he made a mistake letting her go and he wants to get back together. She apparently met with him twice, once when he picked her up by car from the airport and brought her home (I was waiting outside but didn't see him because he dropped her off a bit more in advance) and the other time he had gone to her home to talk to her and clear everything.

I know and I am 110% sure that she in no way cheated on me, or had any physical touch with him because I could see from the messages how much she loves me and how much she cares about me.

When confronted she said that the only reason was that she couldn't just cut him off because she is a really nice person and alwaya hears what others have to say (which is true) and just wanted to hear what he had to say.

I told her that this is too much, because not only has she been texting with him behind my back but he has said clearly she wants her back when he knows she is with me.

The thing that hurts me the most is that she won't block him out of respect for me because that guy still has feelings for her and I consider this quite dangerous towards our relationship as he has made me have bad thoughts and doubt on my girlfriend that she might cheat on me with him.

I just want to know how I can get over these thoughts because I love her and I plan on marrying her and I checked her phone again after a while and she hasn't been talking to him since that day.