Shona Holmes is a Canadian citizen. She suffered from a number of symptoms including dizziness and loss of vision. Her family doctor in Canada sent her for an MRI and the results suggested a brain tumor. Homes might have to wait months before seeing a neurologist for further tests. (This hasn't been confirmed, to my knowledge.)
Shona Holmes decided to fly to the the Mayo Clinic in Scottsdale Arizona. There she was eventually diagnosed as having a Rathke's cleft cyst (RCC) in her brain. This is not a tumor and it is not life-threatening. It does, however, threaten her vision, which was already impaired.
Eventually, after more tests and at least one further visit to Scottsdale, the cyst was removed. It's not clear how long it took from making the first appointment at the clinic to the actual surgery but the article on the Mayo Clinic website suggests it was about a month. Incidentally, this article has been removed from the Mayo Clinic website but it is cached here.
The bottom line is that Holmes suffered from a non-life-threatening cyst that affected her vision and could have eventually led to blindness. She choose not to wait for treatment in Canada but to pay for treatment in Arizona.
Shona Holmes is suing the Government of Ontario in order to force it to revise and/or dismantle public health care. The suit [Lindsay McCreith and Shona Holmes/The Attorney General for the Province of Ontario] is being supported by the Canadian Constitution Foundation, a right-wing group that's described here.
To summarize, we have a patient with a non-life-threatening brain cyst who may or may not have had to wait a long time for treatment in Canada but choose to go to an American clinic where she was operated on after about a month. This patient is sufficiently opposed to Canada's health care system that she has collaborated with a right-wing group to sue the Government of Ontario for allegedly violating her rights.
Oh yes, one more little bit of information, this is the same Shona Holmes you see in this video warning Americans about the dangers of universal health care. This Shona Holmes was going to die of a brain tumor if she had stayed in Canada.
It's pretty clear that Holmes is not telling the truth in the TV ad. The only question is whether she "misinformed" the group Patients United Now or whether they pressured her into making untrue statements in the TV add. Canadian Cynic wants to know [Shona Holmes: Useful idiot or puppetmaster?].