Venting and looking for different perspectives on this situation.

I'm really tired of feeling like I've done something wrong anytime I do something with partner S especially when S visits the home I currently share with M.

I'll try to keep this short but the events of last night are a good example. Sunday I was texting S and trying to organize plans for the week with both M & S. S and I wanted to see each other Wednesday and Saturday. Checked with M and got the 👍. Wednesday is the day me and M usually do an art project with the kids. I didn't want to miss it so asked if S could join us making ornaments. Again I got the go ahead and they seemed excited for S to be visiting. Then come Wednesday and things somehow end up going sideways. M was in a good mood when I got home from work. When S got here M was working on some decor that the kids couldn't help with. Got the kids situated and all the supplies ready. Told M we were getting started. They continued working on the project but did join us for a little while and made a few ornaments. Then went back in the other room. At this point I knew their mood had shifted and at some point they went to their room. Once S left I did confront M and I was annoyed. I said I was tired of feeling like I did something wrong anytime S visits or I go visit them. I was told I had not included them in the activity. 🤯 I don't understand that. I verified that it was OK to spend Wednesday with S. Made sure they were OK with S joining us for art day. They knew S was coming at 3:00 and we would need to do art time right away because S doesn't drive after dark. I let them know when we started not to mention they were right in sight of us and could see all the supplies on the table. I don't really feel I did anything wrong and am really bothered by the situation. They have been in their room since last night and haven't really talked to me since.

I think it's worth mentioning M is 7yrs younger and in their mid 20's. They are neurodivergent dealing with depression and anxiety.