I agree with @carachel2 that this has the feel of a media-induced panic. The fact that your mother has a co-worker who’s doubling down on her only makes it worse. I can imagine a scenario where the co-worker blindsided your mother with all sorts of suggestions that made your mom feel like she was a neglectful parent. Depending on the politics of her workplace, this might be a person who isn’t easy to dismiss with a polite “mind your own business”.
Call the admissions office of the OOS college you want to go to (or colleges if you’re still trying to decide) and ask if they can pull out the big reassurance guns on your behalf. Your mom isn’t the first parent to feel like this and it’s in your future college’s interest to convince her that they’re wonderful. They may have someone with a fancy sounding title give her a personal call or maybe they can enlist local alumni to reassure her.
Good luck.