Wanda's always walked a fine line between helping her teammates and killing them with her uncontrollable "Hex" powers. Like the Witch from Wundagore mountain shows, she's forever been on the edge of losing her mind, a loose cannon capable of accidentally harming friend and foe alike.
Take this exchange between Scarlet Witch and Electro for instance.
Wanda pulls a Vader Force Choke on this poor two-bit villain, and could have easily killed him. It's not the act so much that bothers me, but her teammate's reactions.
Captain America for instance. A guy who has fought in the bloodiest war in history, and has no doubt seen gruesome dismemberments, Nazi torture victims and the like takes one look at Wanda and has a WTF moment.
Rather, it was "What the Blazes?!?!?!", but we know what you meant comics code Cap.
Is that fear in your eyes Steve? His response says it all. "UM.... Yes!" So what do you expect from someone who can bend reality to shape her will, giving birth to mutant twins from an android father, or wiping the mutant gene out of existence.
Or most of the mutants anyway (since we can't just get rid of Marvel's best selling titles!). Still, with that kind of power cap is right to be scared. Scarlet Witch could conceivably do anything, including making Steve Rogers her love slave. SHe wouldn't do that though.... would she?
So in hindsight, the crazy was there to begin with. Brian Michael Bendis just connected the dots.