I totally agree. That is rude to not ask in the first place, she does get some points for having the courtesy to replace the item, BUT, you replace what you took. Not some bargain brand.
There have been times when I have had to borrow an egg or a can of condensed milk from a neighbor (yes Marsha, her.) When I replace it, my policy is, replace it with the brand she used and always give more back. I borrow two eggs, I buy her a carton. I borrowed a can of condensed milk, I replace it with 2. I feel this is the right thing to do. For her kindness and any inconvenience I may cause her in a recipe.