>>279843498 (OP)
Keep her well-secured. Elves are dexterous, they can squirm out of a lot.
Keep her magically sealed. Even ranger-type elves often have a little magic in them.
Don’t gag her. Elves say the darndest things when they’re tied up, and they’re fun to talk to.
And don’t rape her either. It’s more fun that way.