If she is biting that is her signal to back off whatever it is you are doing at the time, don't push her to do something she is not interested in. You have only had her about a month and it takes months to tame a budgie and they do go through phases with their personality as they mature so don't be disappointed. Do I remember correctly that you have a dog and if so is the dog kept away from the bird? The presence of a dog could contribute to the change you have noticed, she may be afraid or startled by the barking of a dog or the sight of one if that is happening. It is recommended that if there are dogs or cats are in the same household as birds that they are kept separate from one another at all times.