My kid had an intern work in 2022, She got W2 with more than 1 thousand income, withhold social security and medicare ,CASDI.
#1 Should she file her tax return for 2022 independently or should she file with her parents (17yrs old)
She can file her own tax return. and by filing her own tax return she will enjoy her own standard deduction as dependent. see https://www.irs.gov/publications/p501#en_US_2022_publink1000221069?
Use freefile on IRS website. https://www.irs.gov/filing/free-file-do-your-federal-taxes-for-free?
You can still claim her as dependent.
#2 Consider her college FA, which way is better?
Doesn't matter. Her $1000 has to be counted as her income no matter how she files the tax. It matters very little.
#3 If she wants to buy IRA with this income, which way is better?
She can put all her earned income into ROTH IRA, because her income tax rate is 0% (see answer #1)