Mr girlfriend needs to ammend her taxes so I can claim her and my daughter. She already has claimed her but we would get a bigger return if I did.. Where to get started

Mr girlfriend already filed her taxes claiming our daughter. We would get back more if I claimed my girlfriend and our daughter. My girlfriend has lives with me for 3 years. Where to get started? How long should I wait to file my taxes claiming my girlfriend and our daughter after she sends in the paper to ammend her taxes? My girlfriend made under 3000 last year.