I'm not sure that under Missouri Law the situation is so clear cut.
Section 565-021states that second degree murder is when a person, "Knowingly causes the death of another person or, with the purpose of causing serious physical injury to another person, causes the death of another person." Drew, while perhaps a despicable human being, Neither set out nor intended to do physical harm to Meier, not in any provable way. Emotionally upset? Perhaps, but the wording is pretty stark here so it would be futile to try and claim Drew's actions were ever intended to be physical in nature.
This section also has a second clause, defining second degree murder as: "Commits or attempts to commit any felony, and, in the perpetration or the attempted perpetration of such felony or in the flight from the perpetration or attempted perpetration of such felony, another person is killed as a result of the perpetration or attempted perpetration of such felony or immediate flight from the perpetration of such felony or attempted perpetration of such felony." You might be able to gain more traction with this approach. However, the only "crime" that Drew was guilty of was the weird "violation of ToS" runaround that was rightly thrown out. If Drew's actions could have somehow been linked to a felony (and I'm sure some RIAA lawyer could figure out that torturous linkage somehow), then you might have been able to chain a second degree murder charge on her this way. As that was never going to happen, the second degree murder case for Drew is nonexistant.
You might be able to pull off a manslaughter charge under section 565-024, Involuntary Manslaughter, if you could prove that Drew's reckless behavior (1st degree) or criminal negligence (2nd degree) brought about Meier's death. Again, though, this is tough to link. Under section 562.016, reckless behavior is defined as a conscious disregard of "a substantial and unjustifiable risk that circumstances exist or that a result will follow, and such disregard constitutes a gross deviation from the standard of care which a reasonable person would exercise in the situation." There are several hurdles here that must be passed and, if Drew were to be convicted under them, that sets an uncomfortable precedent that sort of allows John Gabriel's Greater Internet Fuckwad Theory to become the de facto law of the land and anyone who has ever flamed anyone else might suddenly then be held accountable under law. If we're going to throw up our hands and scream bloody murder when Amazon yanks back a book, crying that they're not the police and don't have a legal right to do that, then enshrining either Facebook/MySpace's ToS or Penny Arcade as the law of the land must surely be equally as abhorrent.
Criminal negligence is much the same, but the wording goes: "he fails to be aware of a substantial and unjustifiable risk...". That "fails to be aware" might be something to hang Drew on if Meier had previous suicide attempts, however it's sort of a Catch 22 argument. Could Drew's actions have pushed Meier over the edge? Certainly, but then, if she's that fragile, couldn't anything have pushed her over the edge? How can you argue the uniqueness of Drew's behavior being the deciding factor?
This is why Missouri chose not to prosecute, which led the Feds to step in and try to Capone Drew, nabbing her on the squirrely ToS violation. It didn't work and shouldn't have worked, but it means Drew gets away, at least from a criminal standpoint, with being a real waste of flesh, water and air. Hopefully, she'll get rammed in civil court.
It also points out the simple fact: Due to a level of informational sharing and processing that we as a civilization have not seen since Hammurabi pointed at a slab of stone and said, "I've got something to say!", our legal system is simply not equipped to handle edge cases that are suddenly not so 'edgy' in terms of the Internet. For instance, what counts as harassment online? Sure, a huge email campaign may be obvious, but a social networking page? Is it the act of creating the page? Is it the continued daily existence of the page? Is it only when the page makes issue of itself? Legally, this is still a pretty gray area. Certainly, Meier's parents should feel free to campaign for rectification of this lack of legal definition, both in Missouri as well as at a federal level. We can even call any modifications to legal statutes that come from it "Megan's laws" so everyone can feel warm and fuzzy about doing...something...for the kids...somehow.
This, of course, will come too late to do anything about Drew. That's life when you're reactionary instead of visionary, though.
The fact of the matter is, though, that we're seeing more and more that our real-world legal system is just not agile enough to deal with online interactions. The question we have to ask is how do we approach this? Do we take our standard approach and slap some more bandage laws on it and then pat ourselves on the back and say "Mission Accomplished!" while doing nothing to address the root causes or do we take a long, hard look at the situation and introduce new legal paradigms specifically designed to address these issues? Call me cynical, but if there were an equivalent to Band-Aids in the legal community, I'd buy a helluva lot of Johnson and Johnson stock because, as a society, we prefer to treat symptoms, not causes.
All standard disclaimers apply (specifically, IANAL, but I have slept with several, and the fact that one shouted, "Bang the gavel, BANG THE GAVEL!"during...let's call them "closing arguments"...well, I think that must give me some sort of cache).