Typically when someone borrow's your vehicle, your insurance company may cover them if they involved in an accident, but in your case, moving violations and citations are charged against the driver and not the vehicle. So the DUI is most likely only going to affect your neice's driving record.

If she were to get into an accident, then your vehicle would be involved and in that case it could effect your insurance rates if there is damages to the vehicles and they have to cover the claim.