Maybe she usually shoot fully automatic and it got bumped into AV mode or something. Anyways, if you agreed to pay her an amount of money for an amount of work, and the work was done, you need to pay her. There's no ground for wasting time in any kind of court try to get out of that, unless there was a clause in the contract/agreement saying that the work had to be up to a certain quality in order to receive payment.
If I go get a job at McDonalds, and they agree to pay me $$/hr, and I show up and work my first full day, they can't just not pay if they think the work was unsatisfactory. They can fire me, they can never work with me again, they can give me bad recommendations, but they can't just not pay for the work that was completed (poorly or not) under the prior agreement.
If she were a good business person, she wouldn't want to get payed full price for work that is poor quality. But that's not your decision to make. Does she know you're unhappy withe the results? That's a good place to start.