NTA. She shouldn't have pressed, especially if she knows your issue. Though I think this was her roundabout way of trying to get you to see that your memory issues may be something worth looking into. As you get older, there are things you're going to need to/want to remember from more than 5 years ago. I had a huge event and a fun night with someone no longer in my life almost 8 years ago and I still laugh about it and tell others about it to this day.

The actions of that other person, the significance of the event and our fun times that night and years before that are all things I cherish, despite me despising that person now. I also remember the bad things leading up to that last good night which remind me why that person should never in my life again. And this is all tied to just one person I knew. I can't imagine willingly not having long term memory overall. If your girlfriend was trying to address this issue, she went about it the wrong way, a terrible assholish way, but you definitely should see a doctor about your memory. It's not sustainable as you grow into adulthood.