Well if she had come over to my house, I'd politely ask her to keep her uneducated opinions back on her own lawn. When I ask for her opinion, I'd rattle her cage. :nyah:
I think for a lot of the older generation, experience with my own relatives anyway, the Christian nature comes out and they remember all of those sermons about the serpents being sent from Satan. I remember my first snake I had, my great-aunt who is a minister told me I was evil-incarnate for keeping such a foul creature. Also the woman who told my mom that getting a divorce was a one-way ticket to eternal damnation..nevermind the fact that my mother's first husband was abusive.
And I think more so nowadays it's just complete ignorance and misunderstanding. They don't think about the role of a snake in nature. They can't get past the fact that they lack legs (kin to worms and bugs, oh my!) and they look cold and wet. However they'd be surprised to feel them as they aren't all that bad.
My own mother is just starting to figure it out. Would she rather have mice in the house eating her cookies or snakes outside with full bellies and a mouseless house?
It's only taken a few years, but when she sees a snake in the yard she either leaves it, dad relocates it to the woods or his barn, or she calls me to come move it. =P
Anyway I wouldn't worry about it too much. She just offered her opinion where it really doesn't matter. You're the mother of your children not her, thank goodness. Enrich their lives as you see fit. =D