Am i the problem for going back on a promise and being upset?

This might be a weird, long, unnecessary one but I need some insight.

I (22F) and my girlfriend, now fiancée (25F) went on a 4 day vacation with Helga (alias, 26F) and my friend Hazel (alias, 20F)

Hazel has irregular period, and she sadly had hers on and off on this vacation. I Promised her I’d go swimming with her on our return day if her period was gone by then.

After I made this promise, a lot of stuff happened. My family decided that they needed a photoshoot that would mix with our leaving date, and we would have absolutely no time to spare before leaving. We also didn’t really have a choice in it, due to the photoshoot being for a Christmas present for my stepmothers mom, who doctors believe to have cancer (not confirmed yet)

Another thing was some ongoing drama with Helga, specifically her making me and my girlfriends proposal (which happened at the vacation house) all about herself, and I had to spend 45 straight after being asked the most important question in my life, to console and apologize for an offhand comment that was made earlier that day. Something about shoes, I’m not quite sure tbh.

So skip to Sunday, and I’ve forgotten all about my promise. Hazels period is gone and she wants to go swimming, but my now fiancée didn’t want to drive 4 hours with wet clothes in the bags, and it would mean we wouldn’t make it to the photoshoot, plus I just wanted to go home. No one really mentioned the promise to me, but they were loitering around, waiting for me to just accept fate and go swimming. It was incredibly awkward and after we left, it wasn’t until we were 20 minutes away from home that I was made aware of the promise, and why everything was so tense.

I apologized the same night, over text and I thought it was solved. Now today, Helga flipped out at me over a small financial thing about the money that was owed for charging her car, roughly 10$, where I let her know I didn’t really have anything to do with that, and to please text my finance as she would be the one to handle that. She got mad, accused me of not taking accountability and just left it like that. Turns out she was upset for my friend, who I thought I had worked everything out with. They had been texting and Helga was just incredibly rude to me which of course upset me since 1) I didn’t know they had been talking about me and 2) I wasn’t denying accountability, it was simply easier for them to work it out than me being a middle man.

My fiancée felt bad that it was all being Put on me, when in reality she was the one who didn’t want wet clothes in the bag and convinced me not to go swimming. She ended up refunding Hazel for about 3/4 of the cost, apologized and sorted everything but I still haven’t heard from Helga and I’m honestly not impressed by how she is handling this, and I’m quite mad

So am I the asshole for not doing what I promised?