Whooo, boy, this article is a hot-button issue! It's difficult to have a reasonable discussion ANYWHERE on the Internet about this, it seems, because the anti-vaxxers and pro-vaxxers often spend more time at each other's throats than actually observing their children to see what's going on...
As a new mother (and one very wary of the medical field for reasons I won't get into now), I say it is important to support your daughter in law's convictions, and to ask her why she chose them. Maybe getting to share why she is choosing what she is choosing will help her think through it, and having someone willing to hear her out is what I would have wanted when I was making this very choice for my first child. Being able to talk about it without someone forcing their opinion might help her think through the pros and cons of either direction!
AND I would like to add, to the Internet at large, that it is VERY EASY to broadcast your strong opinions when you don't have children that are affected by them. I had an unmarried, childless friend lambaste me for the choice I made for my child, not pausing to think that I had prayed, worried, thought about, and struggled with my decision for months because there was an actual living being dependent on me, and not just an argument to win. She was just confident that she was right and I was wrong. This is not a loving way to help a new mother on her path.
Yes I agree a new mother has way too much to worry about. I hope she will follow what is in her heart. Im sorry about your friend it must have hurt alot. Take care.