I think is was very decieving of your sister to ask to borrow your BEAUTIFUL AS trailer knowing full well she would not be there for a few day's.
DON'T. . .DO NOT let her or anyone borrow it again!
Next time just tell them you checked with your AS insurance Co. and they will not cover anyone but you pulling the AS. Which my really be the truth.
I have a 76 31' Sovereign
that need work and I would not let anyone borrow it.
Don't feel bad or feel like a bad person because you put your foot down about the trailer. You worked hard for it and you have paid your sister back for borrowing her Crappy Camper last year. SO you are even.