Hi there Jaymi!
Welcome to OCF! Glad you found us, sorry you had to

Quitting smoking is tough and ChristineB would be the person I would want to handle that question due to her experience there.
Dental work become very problematic after radiation, so she will want to get that addressed before treatment, as afterwards the risk of osteoradionecrosis is very serious.
I know it's pointless to say "don't be afraid" due to the severity of an oral cancer diagnosis caused by smoking, but reducing stress, which reduces cortisol levels in the body, will only help your and your mom's immune system. So breath, find relaxation techniques, and get as much support as you can my dear friend.
Keep your chin up and keep us posted, we're here to help.
Eric