Hi NXK and welcome to you and your mother.
You note the suggestion of a partial removal of the AN plus radiation. Some here (Jim Scott comes to mind first) have had that done. That would be "debulking" the AN (basically, scooping out the core of the AN), then radiating the remaining parts of the growth. I have heard that many doctors are now considering this processes as it can help with facial nerve preservation as well as other reasons.
If you all are researching traveling to the States to have the treatments done, there is massive info. Duke University happens to be top notch on the East Coast. There are many around the country (ie: here in Boston, out in LA, as well as many other terrific surgical treatment centers) that perform terrific work. Many terrific radio-treatment centers as well. I'm not sure if you are looking to have both performed Stateside or just the surgery. It may be a timely/costly concern as the treatment and time to stay in the States may add up substantially. There is a lot of information available here about both forms of treatment, many noted for Stateside. Please use the "search" option here to help narrow down info that you seek out. But, most of all, the research can be overwhelming, so please step back from time to time to absorb the info, then resume your research... so, you don't become too overwhelmed.
Again, welcome to you and your mom. BTW, my boss is from Greece. I tell him that one day, I shall travel there!
Phyl