history: I once called my girlfriend's mother mom by accident. We were only dating for a few months and I felt so awkward but she just laughed it off. I once called my girlfriend's mother mom by accident. Haha_comma_ I'm sorry but I had a little laugh at that. It reminded me of the time I did that to my teacher in school. I was embarrassed_comma_ but it made me feel better to find out that it seems like it's a common thing that happens_comma_ since they're female authority figures that you can easily mix up.
current: Exactly, especially since we were only dating for a few months! I felt so awkward but she just laughed it off.
next: Yeah, she knew what you meant. She probably forgot in two minutes, while you've thought about it for much longer. The best thing to do there is to just show off your sense of humor and ability to make fun of yourself and not take yourself too seriously, which it sounds like maybe you did.