Executors are allowed to spend estate money as they guide the estate through probate – they just can't spend it on themselves. Probate can be an expensive process, and your executor does not have to pay the costs herself. But if she does occasionally use her own money on behalf of the estate, she's entitled to reimbursement. But it's best to check with an attorney first to make sure she's taking money in the proper way.
Your executor is permitted to make expenditures from estate money to cover payment of debts you leave behind, taxes that are due, and the costs of operating your estate. This includes anything from a few dollars spent on postage to hiring an appraiser to value your assets. Your executor can pay your funeral expenses, and she'll probably have to keep current with insurance premiums for policies that cover your major assets. In most states, she must give an accounting to the court of all expenditures at the time she closes the estate.
Probate can be a time-consuming and somewhat difficult job, so executors are typically entitled to compensation for their services. Many states' laws detail exactly how much an executor is entitled to receive. For example, in New Jersey, she gets a commission based on the value of your estate. Executors are typically paid when the estate closes, and the transaction must be approved by the court. Your executor can't arbitrarily take compensation from the estate whenever she likes.