Ge,
I was just diagnosed at the age of 54. My neuro on the first visit delayed the dx because of my age and I would imagine the doctor thinks perhaps your mom is too old too. Please encourage her to be checked by a neurologist - her problems very well could be MS but they also could be something else. Either way, she needs to be treated and not list with all the problems if possible.
Good luck to you and your mom, Lulu
She may have MS and she may not. What I've learn of this disease is that it's sometimes difficult to diagnose because a lot of it's symptoms can be attributed to a ton of other diseases. Since you're family may have a history of MS maybe you should have her be seen by a neurologis and then they can decide if they need to run tests or if her syptoms are atributed to her other pre-existing conditions.
You asked how MS is diagnosed, right? Well, it's usually don'te by doing an MRI and/or a lumbar puncture. But even then the diagnosis may not come if those two tests come back inconclusive. I guess I'm lucky in a small way because atleast I know what's making me sick. Both my MRI and LP came back positive for MS.
I hope this has helped a little. Be there for your mom and continue to do research. This Forum has a ton of useful information. Especially the health pages.
I wish you and your mother the best of luck. I hope she feels better soon.