@Stacylkh
It sounds like you got two letters from the IRS (one for 2018 and one for 2019) " saying not to do anything if you have the rights to claim her". The letter also (usually) said to file an amended return if you did not have that right. Your ex got (usually) the same letter. If neither of you file an amended return, you will both get a 2nd letter from the IRS. At that time, you will have to prove you have the right to claim her, by showing she lives with you and the new court order.
On the other other hand, if the 2nd IRS letter is the one asking for proof, then yes, you now send the IRS your proof,
