MC isn’t scummy. She isn’t trying to blackmail her or anything. She just wants to spend more time with her.
I believe they call her scummy for being a lazy bum who just wants to mooch off her parents and play games all day. And also, more recently, she wants to squeeze even more moolah from 'em to spend it on call girls!
In Asia, this kind of behavior is called being unfilial and it's a very big deal.