Parents, how badly do you think this will go?

The best thing in this situation would be to point this out to your ex and offer to let her have your daughter on Mother's Day. That would look good in the eyes of the court. If you just abide the order and keep your daughter with you on Mother's Day, the ex will use that against you; as you know the judge did not do that on purpose. You need to make an effort to be the bigger person and do what is right, which is letting a mother be with her child on Mother's Day. Take care!