My daughter is 44 years old and has been living with us all of 2020. She has earned $4,600 dollars in various jobs. We have spent more than 7K on her teeth and cover all her living expenses. Would she qualify as a dependent on my taxes?
No---she made too much--she is over the limit of earning more than $4250 for 2020, so you cannot claim her and get the $500 credit for other dependents,
However, it sounds like the only reason why she is not your dependent is because her income was too high. That means you are able to claim her medical expenses on your tax return as an Itemized Deduction. Unfortunately, due to limitations and the high Standard Deduction, it is very possible it won't reduce your taxes.