What happened to my mom?

So I have 3 exams 2morro for summer school. I studied for 45 mins when I got home today so I wouldn't have to later. When I was done I asked if I can go over my neighbors house and she started yelling at me bc I didn't study which I did. She was like "you only studied for 10 seconds!" WTF!?!?! i even told her after i was done with my lunch i was going to go in my room and study she said ok and was all happy. then when i said that she went all physco on me. im just really mad and confused! help me!!!!!!