<human>: I'm still confused at how I'm supposed to react to this and was wondering if you guys on reddit could help me out! Thank you so much for taking the time to read this.

So last year, my girlfriend did a study abroad for 8 months. Her friend that we'll call Albert was living in the same dorm as her and was going to be kicked out of the dorm after the 1st semester ended. He needed a place to stay for 3 days while he was searching for apartments and my girlfriend obliged.

I told her that while I understand that it's unfortunate for Albert, I feel very uncomfortable with this situation. My girlfriend told me that it is fine, there is absolutely nothing between them, and he has a girlfriend. After failing to convince her, I have no choice but to accept it. I told her that although I completely trust her, it still makes me feel very uncomfortable. He stays the 3 nights and I trust her words that nothing happened.

So flash forward 1 year to today. I find out today from my girlfriend that before I was in a relationship with her, some stuff has happened between her and Albert (not sex, but it goes beyond kissing). 

I am pretty shocked by this. She tells me that you can still be normal friends with people and that "nothing happened beyond that". I ask her why she didn't tell me about this before having him spend 3 nights last year and she told me that nothing happened and I shouldn't worry about something so long ago. Well, I am worried about it. 

Is it wrong of me to at least lose some trust in her after this? It was over a year ago, but I think I am justified for how I feel right now. I don't think she cheated that time last year, but I can't help but get thoughts like that in my head. I'm really lost right now. What should I do?

Can you give me a shortened version of the text?
<bot>: Girlfriend left out some important information regarding her past with a guy who she let sleep over at her place and I didn't find out until a year later.