he claimed her on his stimulus can i file her on my tax returns?
You're mixing apples with motor oil here. The stimulus payment you received already is a done deal. You can put it in the past because it means absolutely nothing what-so-ever in any way, shape, form or fashion for your 2019 tax return.
If there will be another stimulus payment in the future, that payment will be based on your most recently filed tax return. If you go online to sign up for the stimulus you *WIILL* *NOT* be able to e-file your return. That's because when you sign up for the stimulus on the IRS website, you are telling the IRS that "I WILL NOT BE FILING A TAX RETURN". So if you sign up on the IRS website, you "WILL* *NOT* be able to e-file your 2020 tax return.
A dependent can only be claimed on one tax return each tax year. Period.
