As a mom of a child with severe nut allergies, I would love to have "most places" be nut free. But the reality is that while any accommodations to do so are wonderful, it's my responsibility to a) determine if I deem it safe even if it's not nut-free, and b) to decide whether or not my child should go, and c) to educate my child on food safety and allergies so that someday he can make those choices/decisions for himself. Some places, bringing our own snacks and cleaning the table/chairs, etc. is enough. Other places, we just don't deem safe at all and don't go (i.e., to AAA baseball games, specific restaurants, etc.). I have been known to ask other parents not to let their child eat their PBJ or granola bar, when there is simply no place to safely move my child or the snacking child apart. But I do it politely. I'm sure someday some parent will go off on me for this, but none has as of yet.
This is a mom's group, and frankly, I'm guessing that some mom's don't even understand what "nut-free" means, or how to prevent issues with nuts. If this were a school, where the government is required by law to provide a "safe educational environment" I could see pitching a fit if there were serious danger. But for a private group of well-meaning moms, no.
Of course, there may be extenuating circumstances to why she is acting this way.