No, the $5 on the W-2 is not something she needs to pay. It is indicating that the restaurant remitted the $5 on her behalf. She does not need to file a tax return, because dependents with income of less than $14,600, or unearned income (like from investments or trusts) of less than $1,300 are not required to do so. The cash tips are income that need to be considered. You can read more about that here: Are Tips Taxable?
Also, I don't know what state you reside in, but please check the instructions for your state's income tax return. Some require filing with any amount of earned income.
Next year, she may have a filing requirement, depending on how much she actually makes. The filing requirement for 2025 is $15,000.
