Hi Kathy,
Good for your mom for being such a fighter! I wish you all the best.
As for the mask fitting and use during radiation, my mom actually had no problem with it. It does seem it can be very confining and if you are not comfortable with that it can be daunting. But she did fine with it personally. Everyone is different though... preparing her for it upfront is definitely a good idea, as well as being armed with an Ativan, or half if she's real sensitive to it like my mom was.