AITAH boss vs. assistant

I thought that I got along pretty well with my boss, she’s done a lot for me and I’ve really enjoyed a lot of my job for the last 2 years.
Now she has been known to sometimes lash out at coworkers, and I know the last person who had my job left because they didn’t get along. But I had only seen things from a distance and it happened so rarely I didn’t think of it, and was just happy we got along.

Until this week! I was asking her a question normally, not upset or frustrated, but she wasn’t following what I was asking, and suddenly out of nowhere she narrows her eyes and wags her finger at me and gets this aggressive tone and says “You’re snapping at me and I don’t like it.” In front of a bunch of people while we were trying to do something! I’ve never been talked to like that at any job I’ve worked at, much less somebody that I had thought I was on amicable terms with for years. I was so confused and offended I just went “ok????” and turned away to try to get through the task we were trying to finish.

I approached her later and apologized and asked if she was ok, and she said I snap at her when I explain things and that she just couldn’t take it. A few times in the past I did notice that after I’d tell her something she’d say “ok…!” Kind of exasperated and smile at me funny but she’d never say anything more. I didn’t know how to respond so I‘d just continue working and trying to show that I was calm and not upset with her. One time it happened I had just been excited to tell her something, so her being upset in these instances felt out of my control.

But maybe it is my fault? I have had problems getting very anxious explaining things, but only with my parents. I am nowhere like that at work but maybe it’s worse than I thought? I just didn’t want to have to explain that to my boss. I feel like I’m either so out of control I don’t know I’m being an asshole or my boss is crazy.