I want to know if my handling of a situation with my mother was the right thing to do.

My mother is 70 and in great health. I am 47 and in pretty good health but am disabled and find it somewhat difficult to walk. She moved to my town to be close to family, and wanted a Walton-like setting, I think. My three youngest are teens and they are doing their own things most of the time. I babysit my two young grandchildren fulltime and am dead by the time my daughter picks them up at the end of the day. My husband works long hours. Nevertheless, we are willingly at my mom's beck and call, and do countless chores for her. We spend as much time with her as we can even though she is frequently rude and becomes irritated by a huge variety of odd things. She can also be a loving, warm and wonderful woman, and a lot of fun to be with. But - we are always on eggshells, wondering if the pleasant time will be broken by some unknown thing which offends her. She also bought a home with a long, steep staircase to the door even though I was in a wheelchair at the time and had to crawl up them. The bannister is wobbly and only on one side, and although I have repeatedly told her that it scares me to go up and down those stairs and asked her to secure the banister or add another (at one point there isn't one on either side), she hasn't ever done that (and can well afford to). So, for all those reasons, we are not at her home as often as she wants. She rarely comes to mine and when she does, she becomes offended if I take time out to deal with a child, answer the phone, or whatever. She works, has a busy and productive life, and and erratic schedule. I never know when she will be home and have found that if I ask if I can come by she will sound strained and say that she has a lot of work to do. Then she complains that she should never have moved here because we ignore her.
I can deal with all of those things without much trouble. However, once every six months or so she has a major falling out with someone or other (a neighbor, co-worker, family member, etc). This time it fell on me again, and rather than being confused and sad as I was prior times, I am fed up.
She loves dogs and has two, which I care for all the time when she is working or out of town. They mean the world to her and she has been looking for a third. I had just one until last week when I was richly blessed with a 2nd, a trained service dog to help me balance. I have a fused ankle, cysts in my bones, and blood clots so am on coumadin. Falls need to be avoided at all costs and I was sooooo happy to get this service dog.
We had dinner with my mom two nights before, and I excitedly texted her as we went to pick up the dog the next day. All was normal and good. The next day I asked her if she wanted to meet her and she said yes. She came outside cheerfully enough, then became stiff, refused to hug me, or even LOOK at the dog. She made a rude comment or two and then marched back inside. My husband and I were left on the sidewalk with our mouths hanging open, saying "what just happened?". In the week since she has sent me formal letters going on about me making choices which she chooses not to include in her life, and has told us not to visit her, that she will not come to our house, etc. anymore because of this dog. No, I am not leaving out any details here...it makes no sense at all. This exceptionally well mannered creature who will help me walk, get out of the house and live a fuller life is the reason my mother is rejecting us all?
When this happened we just said "okay here she goes again - she will be okay in a week or two", but since then I have been getting madder and madder inside. I have not done anything wrong and would never treat anyone - especially her - like that. She will not communicate, go to counseling, or even just talk to me. It hurts so much when she does this, and this time I think I am just fed up.
After a week of my being sweet and understanding, her irrational nastiness today did me in. I thought long and hard and discussed this with my husband before telling her that I was not willing to put up with such rudeness any longer, that I was angry for being put through this when I had done nothing at all wrong, and that I would not be interested in any further contact until she sought me out with civil behavior. I even blocked her from my phone and email so that she will need to talk to me face to face (she sends nasty texts and emails) when she is past this bout of oddness.
I think she is bipolar. However, she is extremely anti-mental health anything. She will never get near a therapist so I know that I will be dealing with this type of behavior for the rest of her life. I can accept that.
I am so mad right now, though. Especially since she hit me with this during a particularly stressful time in my life. And yet, I'm also feeling guilty. Ugh.
I really don't think we will ever be close again, even after she goes back to normal. It is such a shame, but a part of me died. I'm done.