A girl in a 3-year relationship added me to Close Friends after meeting me — am I reading too much into it?

Hi everyone,

I recently went to a wedding and met a girl there. We started talking, but there was no flirting whatsoever; it was more of a friendly conversation. She made it clear to me that she had been in a relationship for three years and that she really loved her boyfriend. She even said that she was a very loyal girl and so on. I told her that I thought that was really nice and quite rare nowadays.

We were sitting at the same table, and she was the only person there I could actually have a normal conversation with. During the conversation, we realized that we had a mutual acquaintance — a girl I had previously had sex with on several occasions. We weren't in a relationship, but we had a sexual history together and had been intimate more than once.

The girl from the wedding said she knew her, although they hadn't talked in a long time despite having been close friends. Anyway, long story short, there was absolutely no chemistry between me and the girl from the wedding that night.

A few days later, the girl from the wedding added me on Instagram. That same night, she posted a story and I noticed that I was on her Close Friends list. Her profile mostly consists of pictures with her boyfriend, by the way.

The picture she posted on her story was, at least from my perspective, somewhat provocative. Maybe I'm overthinking it, maybe I'm not, but basically she was posing in a way that emphasized her butt while still being dressed fairly tastefully. I ignored it. As soon as she told me at the wedding that she loved her boyfriend, I considered it off-limits. If she were single, then sure.

Later, I realized that the two of them are friends, and I started connecting the dots. Is it possible for a girl who showed absolutely no interest in me initially to suddenly become somewhat interested just because this mutual acquaintance told her certain things about me?

I got the impression that they might be competing with each other in some way. The mutual acquaintance has also been bothering me for several days about watching a movie at her place and, as she puts it, "reminiscing about the old days." I've completely lost interest in her.

Honestly, I don't know what to do. I find the girl from the wedding physically attractive, but she's taken. At the same time, it feels like she's deliberately encouraging me to respond to her. Almost as if she's waiting for me to react to her story and reply.

I have a feeling that both of them are playing games with me and testing how I'll react. And the colder I am, the more cunning they seem to become.

What should I do?