Ahhhh that's what he meant, fair enough. For some reason I thought he meant the way she acted when Destiny died. But for sure, Mystique lost her sanity when Irene died.

Well it's not like being sane is a prerequisite to being in the Brotherhood of Evil Mutants hahaha.

Saying that, I think the biggest thing is that Mystique has acted in the same way to any other "weapon" she encountered. Though he does not have a prophecy from Destiny like Rogue, Nightcrawler is arguably as much of a useful weapon. Of the many suitors she has had, few have gotten a second glance.