I would do #3 or 4 - either she stays with a friend that you know & trust and she knows you have spoken to the parents or she comes with you and brings a friend. If you force her to go alone she could make the weekend miserable for you by sulking the whole time but if she has a friend they are likely to just do their own thing and let you enjoy yourself.

My parents left me for the weekend when I was 16 and I had a big party and nearly trashed the house