Does anyone know what this movie is?

I had the tape when I was little but it must have got lost between one of our moves and I don’t remember what it’s called. It has a princess dressed in pink and she goes down into these caves, where some trolls live who are planning to overtake the castle or something, with a silver ball which turns out to be string which she trails along behind her and follows it out at the end maybe? I only have vague memories so that could be wrong.