I think a really good lawyer, which she had, could bargain it down to Manslaughter for Alexandria (beccause she's a Cape and if you're going to charge people with murder when someone dies in a Cape fight, that gets tricky) and 2nd degree Murder with the lowest possible sentence for Tagg, since he's a civilian. Though I'm sure that the PRT if they really wanted her a Hero could pull strings and find a way to knock that down too, in exchange for, basically, what happened.
So yeah, that's my thought on it. It's not something she should have done, the Tagg-Alexandria thing, but I sympathize with where she came from, and I don't particularly cry myself to sleep over the fact that a War Criminal and Psychological Manipulator who was breaking ten times more laws than Taylor was dying.
So the difficulty here is separating moral and legal judgements, and then ideal legal judgement from what would actually happen.