your niece probably filed her own return claiming she was not a dependent on another taxpayer return.
does she meet these tests to be your dependent?
you could claim her as a qualifying child if all these tests are met
• she has the same principal abode as you for more than ½ the tax year. Temporary absences like for school are ignored
• If not a full-time student, under 19 at the end of the tax year. If a full-time student under 24 at the end of the tax year.
• she hasn't provided over ½ his own support
• she didn't file a joint return unless there was no tax liability but merely filing joint to facilitate refund of taxes withheld or estimates paid
or as she could be a qualifying relative if all these tests are met
• her gross income for 2019 is less than $4,200
• you provided over ½ her support
• she isn't a qualifying child of another taxpayer
if you qualify, claim her but you will have to paper file - no way around this. she will have to amend her return to indicate she could be claimed as a dependent. if she doesn't sooner or later both of you will receive a request from the IRS to amend. if neither does that IRS sends a second notice to both asking for proof.
