I am not a psychiatrist but as a family physician I have many patients on antidepressants and I am familiar with the side effects.
My first advice is that she must NOT stop taking the Prozac abruptly or else she will suffer from SSRI withdrawal syndrome. As you probably know, Prozac belongs to a class of antidepressant called Selective Serotonin Reuptake Inhibitors. If she doesn't tolerate Prozac, she should be weaned off SLOWLY. SSRI withdrawal can be very unpleasant- dizziness, racing heart rate, insomnia are the most common symptoms. In serious cases people have suicidal thoughts. One thing is for sure, she will feel worse than she does now.
She should do the tapering with the help of her physician. It sounds like her depression is pretty severe. Her doctor may want to have her take a different medicine while tapering the Prozac