Unless the mutual fund is tax advantaged, like an IRA, then dividends are taxable income even if they are reinvested. The broker will report the dividends to her on a form 1099-DIV. However, if her total income is less than $6200 (or $10,200 in some cases) then no tax is actually owed.
Because state tax laws are different, state tax might be owed. She can prepare a free turbotax return to see if any tax is owed using the Tax Freedom edition, or the Absolute Zero edition, if she files before the deadline.
If your income is less than $31,000, you can file using the TaxFreedom edition, which includes complicated forms not normally included in the "regular" free version of Turbotax. The IRS requires it to be a separate web site. https://turbotax.intuit.com/taxfreedom/