First, I want to thank everyone who read my post yesterday and contacted me to offer help. It's really amazing to feel the community pulling together.
I spoke with my helper yesterday and we had a good talk. She was under the impression that I wasn't pleased with how things had gone for the first day and that had made her nervous about continuing. I let her know that I was quite happy with how things had gone (particularly for a first day).
She's still somewhat worried about Alex's aggressiveness but is willing to give him and us some time to get used to the situation. Winter driving is also a concern but we'll cross that bridge when we get there.
Things are still a little unsettled but I'm no longer worried about having to get someone in right away to replace her.