a disabled clown in training, and mean with it

All the main SE characters have their canon moments of almost falling into the kishin path, but Maka has this trend where people sort of made her corruption arc to being generic 'because she's impulsive and competitive and a girlboss who would seek the madness for power's sake' like Black Star when canonically she's very unique in how you can push her to the brink enough to seek madness: by ripping her safety net from under her: by killing her friends and her father. And when she did gain that power, she wanna use it to get that safety net back, if she ever fell into madness and became a villain, she'd likely be very close to Lusamine or Spinel when she's all about wanting to get her family back. She's clingy like that.

Posting this iconic piece of media that I just NEVER found online isolated except in an archived reddit thread

life is too fleeting for all this worrying

Yes, your friend will "change" if they come out as a system to you. They seem like they're changing because they're trying to unmask around you and let their alters be themselves and not hide amnesia and other aspects of the disorder as much.