There was a girl like this in my class. We were friendly and hadn't worked together, so I thought it would be okay.
She would message another girl and I every day before class to ask when/where the classes were. I hadn't studied in a while, so ignored it, but it soon became clear that she only valued her own time. It takes a minute to look up a timetable, ffs!
It only got worse when we worked together. She was demanding of our time, and a poor team lead. She was taking part in a modelling competition, so wouldn't show up to class, but expect us to meet after. Once, it was the day before my birthday and I had plans. After I waited for her for an hour (and our other teammates had gone home), she called me selfish.
That whole project was left to the last minute because she would refuse to work independently, and could only meet at odd times. There was one day I spent 12+ hours in uni so we could work together - and she was still an hour late.
In the end, she pressured me to cancel an interview and a pre-arranged meeting by guilting me about the amount of work left to do. Half of our project was a rehash of the first part, and the other half I started from scratch. Her section ended up littered with spelling and grammar mistakes, as well as using different fonts and colours to mine.
As if that wasn't bad enough, I later found out she had the gall to tell the head of the course that she ended up doing all of it herself. Luckily, my lecturer didn't believe it, but still - people like this exist. They think education is a competition and although may be friendly, the stress of trying to complete your own studies, while dealing with someone who requires attention and validation - with nothing in return - just isn't worth it.
You didn't snap, btw! I also ignored messages. Sometimes you have to for your own sanity. I mean, once that term was ended, this angrily messaged us asking who had deleted (their own) work off Dropbox. Too much drama, not enough reward. I'd be polite, but make it clear you can't work with her one-on-one.