If the tumor is in her head why did they remove her adrenal glands? I'm going to use an analogy to explain but let me give you a little background first.
By far, most cases of Cushing's Syndrome are exogenous~ meaning they originate "outside" the body. If a person takes corticosteroids to treat a disease, be it anything from cancer to asthma, an excess of those steroids can cause Cushing's. In these cases the patient can normally be weaned off steroids and carry on with life.
On the other hand, with endogenous production~ the steroids are produced by the patient's own body, in excess. We need these steroids, cortisol specifically, to survive, but too much is a very bad thing. In most of these patients a pituitary tumor is the culprit. The pituitary, a tiny pea size gland at the base of the brain, secretes ACTH which signals the adrenal glands (bean sized gland that sit atop the kidneys) to make cortisol. When an ACTH secreting tumor is present in the pituitary it produces an abundance of ACTH and the adrenals overproduce.
In Alex's case the neurosurgeon wasn't able to remove all of the pituitary tumor. She has pituitary hyperplasia; the gland is riddled with fragments of tumor. I've heard it described as "appearing like the marbling of fat in a steak". Because they were unable to remove the source of the ACTH they instead removed the end target, the adrenal glands.
So, here's my analogy: The pituitary is a radio signal tower, it sends out a signal to the radio (in this scenario your adrenal glands). In Alex's case the "signal" was sporadic ( the radio would switch randomly from whisper quiet to pounding decibels). First they did pituitary surgery to try and repair the "tower/signal". It didn't work. They said they could try again but the chance of success was less than 50%. As an added problem, whether or not they could "repair the signal/tower", it was likely that they would to do further permanent damage to the pituitary or surrounding structures (the TV wouldn't work either). The only other available option was removing the adrenal glands, or "throwing away the radio". We chose that option. Life without radio isn't as enjoyable as life with radio but it's better than a radio that gets stuck at high volume and can't be shut off.