Repairing relationship when a boundary was set too harshly

I set a boundary with my Mom while I was angry and then told her I needed to take some time apart from her. This was 3 days ago. She got upset because she needed to dump water out of an old water softener because my husband installed a new one for her several weeks prior. She asked if she could do it and I told her it would be really heavy and to have her friend who was coming by to pick up his dog that she was sitting to help her. She responded that he is her friend, not her handyman and she would get a hauling service to come. Then she cancelled dinner at our house because the hauling service was coming at the time we were supposed to do dinner.

The next day she said her bike my husband put together has been at our house too long and she needed to come get it. I told her I tried to give it to her several times and each time she either said she didn’t have room in her garage or she wanted to wait to get it when the weather cooled off. She came over and handed me his birthday card and the gate clicker to our community. We were supposed to do his birthday dinner Tuesday so her bringing the card was unnecessary.

I emailed her my boundary and said she was passive aggressive and I was not her emergency hotline every time she felt anxious and wanted something immediately and in the future if she didn’t ask for what she needed, I wasn’t going to guess and I wouldn’t engage in the conversation. She wrote a long email back saying I read too much psychology and analyze everyone and then brought up 6 months of times where she was victimized by me. My Dad died in February from Covid and he was the glue that held us all together.

That’s the background. My question is that I don’t want to be estranged from my Mom, but I also don’t want to be walked on consistently. I would like to bring a therapist in to help us sort this out. My husband also needs to be involved at some point because I am constantly in the middle between them (and I allow it). How do I broach this subject without it causing more fighting?