I'm sorry to hear about your mother's diagnosis and her balance issues. As many others point out on this forum, I think its certainly important to get an opinion (or 2 or 3) from high volume centers. Most providers will be happy to review imaging and discuss their impression with you by phone. however, in your mother's case, her age, overall health, and current symptoms are going to weigh heavily in any treatment recommendations thus I believe that an in person consultation with a high volume center would be useful.
I am certainly not a neurosurgeon or a radiation doctor, so this is just my opinion based on what you have shared.
surgery typically helps eliminate vestibular symptoms, but given her age and possible surgical risks, surgery may not be the best option. HOWEVER, age is just a number, and her overall health is the more important factor in making a decision regarding surgery.
With respect to radiation, from what has been recommended to me and hearing other patient's stories, radiation is not a great option for patients with vestibular symptoms (dizziness, balance issues, etc), as these typically do not go away following radiation and sometimes can be exacerbated.
my guess is that observation with interval imaging and some vestibular therapy to help with her balance issues may be the most appropriate, but would strongly encourage you to seek out formal opinions from surgeons and radiation docs that specialize in acoustic neuroma.