Absolutely not, if she advertises a time then she should be sitting by the phone for the duration of that time should I call her, she should keep a bucket by her side in case she needs to pee and have Tesco to deliver her shopping on the off chance she needs to eat.
As for refusing certain clients, the cheek of her, I'm buying her for the 30 minutes and she shouldn't have a say on what happens during that time as I own her