If she receives $400 or more during the year in compensation then she is self-employed and must file a Schedule C with your personal tax return.
Any items she buys for use by the business can be entered as an expense. However, if the item can be used for both personal use and business use then only the percentage of business use can be deducted from the self-employment income.
IRS website for self-employed individuals - https://www.irs.gov/businesses/small-businesses-self-employed/self-employed-individuals-tax-center
