Anti-Vaxxer

I've got an acquaintance who has gone full anti-vaxx with her 20 month old little girl, posting proudly about this "healthy" decision on Facebook and advocating strongly for her approach.  Others have posted arguments for and against this, and as someone who strongly believes in vaccination I'm tempted to chime in as well, just to ask "Why would you let your kid getting a disease you didn't have because you were vaccinated?"

But seeing as we're not really friend-friends, I don't have kids of my own, and she seems to have all the answers she wants to hear, I'm hesitant before putting my foot in my mouth and going full on confrontation mode - and most likely losing a Facebook friend (or more, depends how it goes). It's her kid after all so she can do what she likes, who am I to say otherwise?

On the flip side staying silent feels wrong too. What would you do?