I suffer Migraines as well and I know how awful it truly is. I have learned over the years. That I need to not get so stressed out over things I cannot control. Yes you are only human, and we make mistakes.
Try and look at things from her side. She was just scared that someone would steal her dog, she lost control out of fear. Maybe she has had some past experiences and has a hard time trusting people. 
Anyways.......I am sure this will all be under the rug by tomorrow after she calms down. maybe she was just having a bad day and that was just her escape was to blow up at you. 
I am sure she is feeling bad about losing control. 
Take a deep breath and don't
let this upset you, it isn't worth it!