My mom lives with me and I let her drive my car...I always put gas in my car and I don't like her to spend her money so she does it and I say oh mom you didn't have to do that I was going to put gas in...she gets mad curses me out and says I'm ungrateful!!! How? Someone please help me understand!!! :-( She stresses me out 6 days of the week!! I just can't stop crying....I'm pissed!

Update: I did say thank you from the jump. She always throws what she do up so I don't like her to do that.