I agree with Byz - is there a way to get a different care giver?

I think you should lay out some guidelines. Tell this person they are not allowed on the computer anymore. Also make a list of things you feel aren't getting done appropriately. I would also indicate what may happen if she does not meet these expectations - say you'll complain to the company you're hiring her through (if that's the case), or if you're employing her yourself tell her you may have to find someone else who CAN meet this requirements if she cant pull through.

I hope you can get this situation fixed =)