Co Parenting

My husband and I have been separated since the first week of October, we have an almost 4 year old son.

He has been with his girlfriend since sometime in September 🙃

He took it upon himself to introduce our son to his girlfriend this weekend, my son has been struggling terribly with his emotions and his anger since the split and this situation put him in a really rough place.

My husband thinks it is unreasonable that I would like to meet his girlfriend and discuss boundaries since he is forcing her into my sons life.

Thoughts? Advice?