They don't have to file if they only have W2 income under 14,600 (2024) but can file to get back any withholding taken out in boxes 2 or 17. But you don't get boxes 4 or 6 back. If they got a 1099Misc or 1099NEC they have to file it as self employment income no matter how small the amount.
You can claim her if she is under 19 or under 24 and a full time student. Did she graduate High School or College? If she graduated in the spring she might meet the full time student requirement.
Who can you claim
https://ttlc.intuit.com/community/credits-and-deductions/help/who-can-i-claim-as-my-dependent/01/267...
