Well with the Phoenix force she beat Apocalypse with a thought so she is the most powerful being(or at least one of the most powerful) in the ultimate universe and without the phoenix force she still is one of the most powerful mutants in the world and was the leader of half of the mutant population
I suspected it was something like that. So it really was the fact that the two most powerful telepaths of their respective worlds tried to read each others minds and got more than they bargained. And this current Jean hasn't even gone near the phoenix yet. Who knows what she might be capable of.
and if you do a story with her it would be awesome
.......I've considered it. Who knows?
I have to find the right inspiration, though what happened in this comic came close.