It always amazes me when people are surprised that someone acted their age.
Like a while back when someone posted, shocked and appalled, that her 12-year-old had the nerve to lose $100 wandering around the mall by herself.
She's 18. My little brother is 20 and he's still snotty as hell. I remember being that way when I was that age. What did you expect?
Doesn't make her right. She should have been grateful. But you did overreact. You could have said to her, "Sister, that's so not the way you should be acting when someone does something nice for you." She probably would have realized her error right then.
She's sorry,, she's apologizing, let this go, give her the phone. No reason to drag it out.