Danielle -
I think your mother will find the G tube will be the best way to maintain a consistent caloric intake. The increased availability of nutrition should help her body elevate some of the other issues she is probably dealing with. Hopefully, the tube will be a short term necessity and she can move forward without it if the throat stretching and scar tissue removal is successful.
You may want to have her have her thyroid levels checked, (if she received radiation to her throat). Radiation and chemotherapy are a harsh but effective way to eliminate the cancer from our bodies. However, the resulting damage to surrounding tissue and organs may result in other issues long after being declared "cancer free"
Unfortunately, one of the hardest things to deal with when using a G Tube or PEG long term, is missing the act of eating. Sounds a little silly, but, she may miss the taste, feeling, and all the social benefits of sharing a meal with friends and family. (Hopefully, this will not be the case for your mother.)
Good Luck and please be extra vigilant for any signs of aspiration