Having worked as a psychotherapist, I perspective that I've seen is that almost anyone can resist being 'cured'. While I can't say that this is the case with your mom, it can be instructive to look at.
Often there is a "secondary gain" (i.e., they get something out of maintaining the symptom). It takes honesty to face up to that. Perhaps it's attention. The theraputic trick is to see if they'll be willing to give up the "gain" or get it some other way. I often go at it as "Would it be OK with you for the symptom to disappear?" and follow up with "Do you think you'd lose anything by the symptom disappearing?" You absolutely cannot accuse them of (essentially) malingering.
