[@Pair of Hearts]
So their character had time to win numerous tournaments, work to afford medical bills, hates their father for apparently doing nothing...

There is way too much that can be believable. A character like that would be an emotional and social mess as they wouldn't have time nor encouragement to do well. However if you want to lighten the mood of the RP you can request that and it's your right to.

As for her stubborn attitude, if that's what she feels than she shouldn't be one that you need to concern yourself with. She's placed her own persona into a character, isn't fluid to change and in the long run she'll be someone that will drive an RP downwards because she wants it to go a certain direction even if it's not right.

One last point I'll mention is that if you go for a generic trope, like mother's death, then you have to spend more effort in building up that character. So many people can't do this and their characters end up being unbelievable cardboard cutouts.