Definitely shouldn't have gone before Cameron or Jennie. Or Marie, come to that. (I reserve judgement on Jane. But I freely admit I'm voting for the pros, really, and Tony can still blow Mark off the floor.) I would have given her at least one more Smooth/Standard dance to see if she really can't hack it outside Latin (and her Latin did have technical problems, too).
And while yes, it's Mark's job to teach her the dance, he's trying to do in a week what most pros in pro/am have months or years to do. And there is only so much he can do in the performance--he can TRY to hold her back from trying to charge out or "lead" him, but he can only go so far without trashing the whole performance.