Maura, I have no experience with an obturator but I'm heartened reading Chris and Cheryl's posts: things WILL improve for your mother.

The radiation is going to be tough, no question. Especially given your mom's ongoing problems with her lungs, with speech and eating and all the rest. You're going to be vitally important to her during this period and afterward, just as you are now. The doctors may well suggest that she get a PEG tube prior to radiation, something I decided not to do but ended up regretting. (I don't know anything about obturators and how that relates to a PEG of course). So if that's an option I really recommend it.

Please use this forum any time you feel like it. We're all here to help, even if it's just to listen. Your mother is lucky to have you, and even if she seems distant I know that she realizes this. Hang in there. You're a very courageous and loving person.