First she just altered probability small scale wise. Like short circuiting ultron or something.
Then she learned a bit of witchcraft or chaos magic. Then we find out her powers were channelling chaos magic the entire time. Then there was something about being a nexus point for all mystical energies.
THEN Bendis came along and said chaos magic wasn't real and she was just a reality warper out of control.
Now no one knows what her powers are.
I like my head canon to be the nexus thing, that she is a nexus for all sorts of energies and she doesn't know how to access it properly. That probably includes quantum probabilities in the original and then switched to chthon's chaos magic after he possessed her. That's why the elder god types want to possess her so they can amplify their powers thru her.