I have never seen the show, so I must ask. Has she ever given any indication that she wants to "escape" this lifestyle? Certainly she knew her husband's (and his family's) beliefs before going into the marriage. I mean I've never seen the show and I know who they are and what they believe. Was the marriage pre-arranged and that is why she has been forced into a lifestyle from which she must escape?
Again. I don't understand why it is so sad. It isn't a choice I would make, but it isn't up to me to dictate the choices that family makes. Also, should something happen to the mom I would not have to live with the consequences, and I am sure they understand those consequences. Frankly, I admire anyone who sticks to their convictions -- especially when it is hard to do so -- even when I do not share those convictions.
Also, I know 3 "quiver-full" families, and they are all lovely people with extremely nice and caring children.