I'm going to say that given the circumstances of her being the adoptive mother of an adult woman, mentioned as aging in-canon, and having grey hair, her getting glasses is probably meant as a way to show she's older without creating new facial models that are going to take up time and resources for a major game, for a single, fairly secondary NPC. Facial models and features that are of going to be of limited appeal and use for the average player, since it's not typical for someone who's decided to play a catgirl to play an elderly or middle-aged catgirl. Glasses are shorthand- your eyesight gets worse as you age, and you're more likely to need glasses at all. Makes more sense than "it's their fetish", seriously.
