A: I'm not sure what's humiliating about being asked to train someone less qualified than you. (Duh, that's why you're training her.)
If you're having to spend too much work time going over the basics with the trainee, see if a class or self-study could get her up to speed. Assigning her simple tasks could help her learn while supporting you. Or ask your manager if those project leads can lend their expertise (read: time), too.
If your issue is that she's "elderly" — would training someone younger annoy you this much? — get used to it. The average retirement age is increasing yearly. Might be she has a mortgage, too.
Karla L. Miller writes an advice column on navigating the modern workplace. Each week she will answer one or two questions from readers. Miller has written for and edited tax publications for 16 years, most recently for the accounting firm KPMG's Washington National Tax office. You can find her on Twitter, @KarlaAtWork.