Just to add a little thought to Melanie's suggestion - I think I might be a little offended if someone (other than my parents or closest friends) bought me a book on parenting. (Maybe I'm a little sensitive! ) But I would gladly take a book recommendation -ie. "I just read this great book at the library called "blahblahblah" and really loved it! I'd highly recommend it, it's so useful for these parenting dilemmas. etc, etc." Of course, you do have to know of a good book then, , but at least you don't have to shell out the money for it, and if she is interested, she'll pursue it.
The other thing is, if all the other mums are becoming offended and avoiding her at playgroup, she will not feel welcome, and will cease to come, I'd guess. Which is really too bad for her and her son - he's going to need help! Gradeschool will be one thing, just wait until he's 16! But you will no longer have to worry about Smee's safety!
Hope your next meeting goes better!