for those still committed to monogamous relationships: if you've been in a situation where you're talking with a few people that could be romantic interests, how do you let them know it's not gonna happen once you've found the (current) one ?

I've been in a relationship with my current girlfriend for almost a year now, and things seem rough right now because of an issue we're having.

My girlfriend is upset with me because she thinks I don't care about her past trauma. She's told me, very roughly, what she's gone through, and I told her that whenever she's ready to talk about it, I absolutely will. But according to her, the last time she tried to initiate talking about it, I told her that I had no idea what to say. And this upset her and stonewalled the discussion.

I don't doubt that happened. My problem is, is that if she were to try again, I might just very well do the same thing. I have zero idea on how to handle something of this severity. How do I ask her to talk about it? Is that something I should be asking? What does someone even say when given this information? I am not equipped whatsoever to deal with information of this magnitude and I'm at a loss. How do I let her know that I really do care about her, and am 100% willing to listen to what she has to say? I worry I'm too far in the doghouse to even make use of any of this advice, but any help is immensely appreciated

Edit in case anyone was interested: We talked and we're okay :). She told me what she went through and I didn't handle it nearly as bad as I worried I was going to. Thanks everyone for your kind words and helpful advice.

I recently went through some old boxes and found my collection of mementos - birthday cards, love letters, ticket stubs, etc. - from years gone by. I'm not convinced marriage will ever be for me, but I've always imagined if I were to get to that point, I'd want to show such a collection to my SO as a way for them to fully understand my story, so to speak. On the one hand, I think of it as a pretty powerful expression of trust in your partner... but I realize the potential for that to massively backfire by introducing jealousy and insecurities. At the same time, I'm very strongly of the belief that what is shared within a relationship is not to be shared with others outside it without mutual consent. I hate gossip, and have had my share of conflict throughout the years over desiring more privacy and discretion in my various SO's conversations with their friends and family about us. That means I would probably choose to leave aside certain things out of respect for my exes, but then I'm not sure if that devalues the gesture.

Any thoughts?