Mystique and Professor X’s history

Mystique is the character most of the fans want gone, and that is because of the inconsistencies concerning the character within the second trilogy. Mutant and proud? A hero? Jennifer Lawrence shoeing it in?
However, there is a bigger problem when the first trilogy is connected with the second one – she and Professor X were as close as if they were brother and sister! And that is not addressed in any way in the original trilogy. If Charles can say that he and Erik have a history together, why can’t he acknowledge that he and Mystique also share a past?!?
And this is one of the biggest problems of them all – I cannot see this version of Mystique, after three movies, doing her best to kill the professor, as she did in the first three movies. I just can’t. And I can’t blame it all on the whole history has changed thing – after all, First Class features a cameo of the original Mystique, thus connecting the two trilogies to an even greater extent.
And if Mystique and Magneto have been friends for so long, why does he cast her away as soon as her powers are stripped in Last Stand?!?
