<human>: Condense the text into a few key points

Obligatory happened a few months ago and I just remembered this while thinking back on all of the horrific moments in my life, as we do. My girlfriend and I are both girls so we don't have problems talking to each other about attractive girls we see on the street, since we're almost always in agreement. We're both in our early twenties. Her mom is like... fifty-ish? Anyway, their family went on vacation to the beach this past summer and my gf sent me a selfie of herself and her brother in front of a building with a large glass window, and in the reflection of the glass I could see two kind of fuzzy figures talking to each other. I could tell both were women but the one was wearing sunglasses and had her head turned so it was hard to get a good look at her face, but she was wearing a bikini. I texted back jokingly about the girl in the reflection; pretty sure I said something like "Who's the hot girl in the bikini?" thinking my girlfriend would get a good laugh out of me noticing some attractive stranger's boobs and then would agree that she was hot.

Instead, she texted back "That's Mom." I realized immediately that the other woman in the reflection was a family friend of theirs who had gone with them and that I am a massive dumbass who should've recognized Family Friend (who was much easier to see but wasn't exactly my focus at the time) and then realized Bikini Girl must be my gf's mom. I thought her mom was a younger stranger because she was kind of hard to see, wasn't looking toward the glass and was wearing sunglasses, and the boobs were... not fifty year old boobs. Then I remembered her mom had a boob job a while back.

My girlfriend and I have been together for a long time so we're used to doing embarrassing things in front of each other and then teasing each other about them occasionally, but this is the one we don't talk about. This one crossed a line. I am very close with her family. And I swear I'm not attracted to my 21-year-old girlfriend's 50-year-old mother.
<bot>: Saw gf's mom's reflection in a window in my girlfriend's texted selfie; commented on the hot stranger with nice boobs to my gf. Got a "That's Mom." text in response and was mortified.