Opinion:
"Generational differences" doesn't necessarily "scream age discrimination." Instead, it very well may suggest that she is not trained, nor has taken the effort, to keep up with adaptions necessary in today's work environments.
For example, and, only intended as a possible theory, Microsoft didn't even go public until 1986. Your Mom was twenty-nine, and her college days were probably over; unless she DID learn the various programs as they surfaced.
I received my degree in 1974, when Bates and Jobs were still pretty much fooling around in their parents' garages. I was trained how to use electric typewriters. By the time the first WP program and PCs surfaced, I had already learned how to use ATEX. The problem was that ATEX was utilized only by media. I didn't even buy a PC until the early '90s. I never had "formal training." Anything I have learned is strictly bits and pieces. Job duty requirements progressed since my first job -- and I had to keep up with them.
If your Mom is not able to complete what would be considered basic assignments in today's workforce, regardless if they are computer oriented or not, that could be what the employer meant by "generational differences." It would probably come across as a valid reason, albeit a tacky expression.
My employer could also term me for only being able to speak English, German and French -- but not Spanish. I would hardly have grounds to claim discrimination based on national origin. My national origin has nothing to do with my inability to speak the language.
Your Mom's best bet would be to have an attorney review her situation.
I am providing an opinion based solely upon your post. For legal advice regarding your specific situation, contact an attorney.