AITA for turning down a birthday invitation after realizing I was only invited to help cover the cost?

I thought I was finally being included, but what I found out next made me feel like I was never actually wanted there in the first place.

I’ve been working at my company for about two years. My department has around 20 people, including supervisors and our manager. I’m friendly with everyone, but I’m not one of those people who builds their entire social life around work. That said, I’m not antisocial either. If people invite me to something outside the office, I’m usually happy to go. I had a great time at our Christmas party, for example.

One of my coworkers, who I’ll call Sally, has been at the company for around nine months, and we’ve always gotten along just fine. Nothing especially close, but totally pleasant. Before the Christmas break, I overheard a few people in the office talking about how they’d been invited to Sally’s birthday party through Facebook. I noticed I hadn’t been invited, but honestly, it didn’t bother me. Not everyone has to invite everyone, and I didn’t take it personally.

Then a couple of days ago, I suddenly got a Facebook notification that Sally had invited me to the party.

I checked the date, saw I was free, and RSVP’d yes. I figured maybe she had just gotten around to it late, and I was actually looking forward to going. The next day at work, Sally came over to chat and said she was sorry for not inviting me sooner, but she “didn’t know I had Facebook.” That already felt a little strange, because we had literally been Facebook friends for months. But I didn’t want to make it awkward, so I just told her it was fine and that I was looking forward to the party.

A few hours later, everything changed.

At lunch, one of the coworkers who had been invited from the beginning pulled me aside to talk privately. She told me she had seen that I was now marked as going and felt like I should know something before I showed up. She said that in a group chat she was in with Sally and some of the other guests, Sally had talked about being “forced” to invite extra people so she could cover the cost of the venue.

Then she said Sally had specifically mentioned me by name.

Apparently, Sally said she “wouldn’t do it unless she was absolutely desperate.”

And this wasn’t rumor or office gossip. My coworker actually showed me the messages.

The second I saw that, I felt humiliated.

From my point of view, this wasn’t a real invitation at all. I wasn’t being invited because she wanted me there. I was being added as a backup body because she needed more people to justify the venue costs, and maybe more gifts or more value brought into the event. That stung way more than simply not being invited in the first place.

So I immediately changed my RSVP and removed myself from the party.

Later, when I was leaving work, Sally asked why I wasn’t going anymore. I told her I had realized it wasn’t going to be an evening I would enjoy. And that’s when the fake smile dropped completely. She snapped at me that no one liked me anyway and that her friends would be shocked that she even knew someone as vile as me.

Honestly, that only confirmed everything.

In that moment, I felt like I had made the right choice. If anything, I felt relieved that I found out before wasting my time showing up somewhere I was clearly unwanted. I don’t feel bad for not going. I feel bad that for a brief moment, I believed the invitation was genuine.

Looking back, I don’t think this was ever really about a party. It was about basic respect. I can handle not being included. What I can’t respect is being treated like a seat filler, a prop, or someone useful only when extra numbers are needed. And once she showed her real feelings, I stopped wondering whether I had misread the situation.

So now I’m asking: was I wrong for backing out the second I found out the truth, or was I right to refuse to be used?