You are correct. There's a weird, but fine,one between transformative work and fanart. You can take commissions for fanart as you're more or less directing more people to buy the IP, and if not, derivative art is easier to do for art. The written word? Not so much. You brought up a good point: this Aiden can land in big fucking trouble.
My guess is that she, like other Aidens, either don't have a good relationship with their parents or is that unstable she needs to be monitored on what she buys. 18 year olds these days usually aren't reckless with spending - aside from student loans that is.
Dealing with anger issues may well be due to her taking testosterone.