Engagement Imploded after visit from mother on Mother's Day

Hello I'm looking for some input (or validation) of my feelings about this terrible split up of my engagement. I try to be supportive/protective of SO but her actions just seem so far beyond what is acceptable.

My mother visited for Mother's Day. My SO was experiencing a lot of stress up to the day that my mother was supposed to arrive because she "dislikes guests" and felt that my mother would judge her on the cleanliness of her house. (mother has never said a single negative thing regarding cleanliness)

Mother shows up and the trip becomes tense when SO gets home. Neither my mother or SO enjoyed themselves. After mother went home she called and expressed feelings that SO didn't want her there and that she had changed from previous visits.

SO blew up, gave me the ring back and went to room to cry. Later in the evening she tried to convince me that we can work it out but only if my mom stays in a hotel from now on when she visits. I said no. I want my mother to be able to feel welcome in my own home.

SO screams in my face, tried to lock me into the apartment, and even grabbed me, all in an effort to take her back. Obviously I said no and left, due to feeling unsafe.

SO's mom calls me angry the next day saying that I didn't protect her, and that I shouldn't have left. SO's mom said that all of this was due to her underlying mental health conditions, which is true but is my fear not valid?

SO invites me back to apartment to "talk" I agreed, and only asked her not to scream/lock me in and remain peaceful. She pulls out a 3-5 page story she wrote about how terrible my mother is, and shortly after goes into another episode of screaming/grabbing me/trying to make me stay.

Today SO wants to put the pieces back together and try to work things out. SO claims that I subjected her to way too much stress (my mom staying for 20 hours) and that is why these episodes are happening.

SO complains that it is as if I don't care about the 3ish years we were together and I don't even want to try, but this just seems like it is beyond repair to me, and honestly I'm done.

My mom is not a bad person. She is older so she can be a little quirky and old fashioned in a lot of ways but she never once said anything cruel or hateful to SO. SO claims she is jealous and "just wants me for herself" but my mom literally only visits every 2-3 months and only stayed 20 hours in total.

I feel as though if I continue to date this girl she'll eventually try to force my mother out of our lives. My mother is the only family I really have and it is heartbreaking to see.

And even if my mother is wrong and she misinterpreted the visit, SOs actions during the breakup were very hostile and I don't think I want to deal with that.