M.C.
Yes it matters which car she is driving. If she drives YOUR car, she may need to be added to your car insurance. It depends on the insurance.
If she is driving YOUR car and causes an accident, YOUR insurance would pay the damages and any dr. bills. If another driver caused the accident, their insurance would cover your car and her bills.
I don't know about the workman's comp aspect. There is a website called lawyers.com that I believe you can pose questions to and receive an answer.
M.