NTA for telling her how you feel. However, there will be times in your life where you will do things for other people even though you don’t want to. If your willing to do crazy things for best friends (at 16 I suspect you’ve probably done it at least once by now), then there should no harm in taking your mom’s arm and walk her down the aisle purely for her benefit, even if you personally think you may be asked to do it again later.