If she is an employee, she can contribute up to her compensation from working, which is defined as her W-2 box 1 wages minus any amount in box 11.
Any excess contributions will be assessed a 6% penalty this year and every year after, as long as the excess remains in the Roth IRA. To remove the excess, contact the Roth IRA and request a removal of excess, this is a special procedure, not a regular withdrawal. She must withdraw the excess contributions AND any earnings that are attributable to the excess contribution. Because this is a Roth IRA, removal of the excess contribution is not taxable, but the earnings are reported as miscellaneous taxable "other income" on her 2024 return, even if the earnings are not actually paid out until 2025.
With earned income from a job of $1800, she would not actually owe income tax because that is far below the standard deduction. She might owe income tax if, in addition to the wages, she has more than $450 of unearned income (interest, dividends, gambling, or other income). This is because a child's investments can be taxed at a higher rate, to prevent parents from avoiding tax on their investments by putting them in their childrens' names.
