She wants to get croissants, so I assumed she wanted to sit for a few minutes in Starbucks. Then she throws it at my face that I told her I was tired of not getting home before 4:00 on other days because we were out having lunch, doing errands, etc. I said that Starbuck's was just a quick stop. She kept going on and on about it, making sure to make me feel bad about what I had said. Every time I try to do something nice, it turns into a rant about something, like she won't drop it, but wants to dig in harder. I finally just end up leaving, so a nice get together tuns into an angry get together.
Is your mom normally reasonable and pleasant or normally cranky? Is she suffering from pain?
Have you noticed any mental decline? I know that when my cousin, who first started with dementia symptoms, I didn't know what was going on. She would disagree with me about anything. Every conversation was of her getting upset over nothing. In hind sight, I see how it was actually her brain changing and she wasn't responsible. I ended up walking out on her a lot, because you couldn't reason with her. Later, I hate it was like that, but, I just didn't know.
If your mom is just being unreasonable to be unreasonable, I might discuss it with her doctor to see if she has a UTI, cognitive decline or depression. All you can do, is all you can do. You can't make her happy if she's either unable to be or chooses not to be.
Sometimes it is easier to just say "Mom, you are right" so then she would shut down the argument, hopefully.
Does Mom have a chance to be around anyone her own age? Any senior centers nearby or would she dig in her heels and not go.... or say "that's for old people". Wouldn't it be great if she made some new friends, to give her something else to talk about.
Have you tried asking her why she is doing this? "Mom, it seems like lately we get into arguments no matter what. Can you think of why that is?"
Why she is doing this might help determine how to react to it. For example, if she has an illness or pain that might deserve a different response than if she has always been crabby.
Can you take the wind out of her sails by agreeing with her? "You are right, Mom. I did complain about not getting home early enough. But today I'm willing to relax a little over a croissant. Is that OK, or would you rather take them home?"
You certainly don't have to put up with her crabbiness. But if the cause is something like depression (which often manifests as anger) or mental decline or pain you might also want to try to help her while you are protecting yourself.
Or give her a Snicker's bar.
It's called ANGER ADDICTION, now exacerbated by aging, medical conditions, and a controlling personality. It just gets worse and worse as these things contribute to the addiction. She's always had a bit of an angry, disagreeable personality, because she always had to be "right!" That's classic sign of a controlling personality. Scenarios are invented to control an outcome so she can be right, to push buttons, be disagreeable, create anger, to feed her constant addiction. The best thing you can do for yourself is learn to understand this disorder, how to deal with it. (Anger addiction, controlling personality, manipulation) That's exactly what I did and it's helped me tremendously with my now 96 year old grandmother who has given me plenty of grief throughout my life! I only found a particular book a couple of years ago when I began to learn more about myself, and then several others through self-help, was struggling to make a new life and was not going to let anyone emotionally abuse me again. It's called "Controlling People" by Patricia Evans. She has a series of books I found insightful. Best of luck to you. You must always take care of yourself first!