yes, it can flip, but I would have VERY good records to document that she supported more than half her support - that would mean she would be eligible to collect the stimulus and it is going to look "odd", but with the right documentation justified, that she was a dependent in 2019 and 2021, but she was not a dependent the one year that the stimulus was paid out!!!! She is otherwise not eligible for the stimulus.
how are you determining that she paid more than half her support? who paid for college? who paid rent, utilities, food, car, insurance...... how much she earned doesn't matter. it's who paid for support
did she live with your all year? and 'live with your' would include temporary time away at college.
suggest filling out the attached and maintaining the supporting documents if she is ever questioned by the IRS.
https://apps.irs.gov/app/vita/content/globalmedia/teacher/worksheet_for_determining_support_4012.pdf
does that help?
