The IRS says that she can deduct all ordinary and necessary expenses for her self-employed work.
The type of expenses will depend on the nature of her work. She'll need to keep receipts of expenses paid.
For business mileage, she can count mileage between work sites and between worksites and other work related places. Mileage between home and the first worksite of the day and between the last worksite back home is counted as commuting miles and cannot be claimed as a business expense.
Please read this TurboTax article for more information.