Vanity Fair tracked down the actual Ermahgerd girl, now a grown Ermahgerd woman who's about as perplexed by the whole thing as you might expect:
“I just can't believe this is my 15 minutes of fame—I was hoping it would come in another form. But I guess you have to take what you can get.”
WTF is Ermahgerd? Gert erducurted.
[L]ike many other Internet memes, the mechanism behind ermahgerd is rooted in the centuries-old tradition of language games, such as gibberish and pig Latin, which have been practiced in English-speaking countries as early as the late 19th century. Both games involve shifting consonants and adding extra vowels in a sentence to cipher a message...
"Meme" culture [without getting into how this terminology bastardizes the concept of memetics] is aggressively dadaistic, the sort of cultural practice that's designed to be instantly and intensely polarizing. If you're not in on the joke -- and it is a very complicated joke -- it's not just baffling, but alienating. If you are in on the joke, it's irresistible: having cracked the code, it's impossible not to participate.
Ermahgerd, and related species of Internet weirdness, tend to get cited as evidence of a deep and irrevocable social rupture -- largely generational, but also unmistakably class-related -- over technology. Some of us, goes the critique, are so obsessed with our devices, so absorbed in digital culture, that our consciousness and personality have been permanently altered, in a way that's more or less without historical precedent. There may be some truth to that. But it's worth remembering that the deployment of elaborate in-jokes as a social sorting mechanism is nothing new, and fundamentally nothing to do with technology.
...The truth is, we all have a desire to cipher and decipher messages in our everyday conversations -- whether it's about a young woman who loves her books, or a pug going crazy over a bone made of milk.
Almost by definition, language games create an inside and an outside. Which group you fall into depends on your ability and willingness to sort through an outwardly meaningless grab-bag of unfamiliar references and puzzle out the grammar, the structural logic, that binds them together. This, and the fact that Maggie Goldenberger was herself performing a joke persona of her own invention when she posed for what would become the Ermahgerd image, makes it extremely interesting that Goldenberger (and also, as it turns out, R.L. Stine) seems to feel very much on the 'outside' of this joke.