As immortalists, I automatically assume we are all also futurists and that we are interested in influencing the future of medicine.
There may be other ways that won't cause her injury to treat the cancer, or she may just not want to live with the consequences of the treatment. I've heard some cause (permanent?) cognitive impairments, accelerated aging, and other things of that nature. While I don't see her asking for cryonics instead of treatments that may cause permanent harm, she may not be the same person after the treatments as before if she has such side effects and may not even be able to see her former perspective on the matter. We all want her to live, but I think any cryonicist might want the right to die in better health if faced with this kind of thing.
Alternatively, we could find all manner of ways to fix or treat the side effects.
Stuff like this is tough to call though... especially when she lacks a voice in the article and we don't know the mechanics of her motivations. Her mother seems to support her decision too.