If you try searching by keywords you find that she tweeted a prayer to the Sandy Hook victims. The belief that there are victims is incompatible with the "truther" notion that it was a fake and all the kids are alive.

Not entirely.

Theoretically, the incompatible notions are that there was no attack and there was it.

You could theoretically admit the existence of an attack and yet deny parts of the official versions, including the numbers or identities of victims.

A much larger and more important space, you could theoretically admit the existence of an attack but not the lone wolf authorship of Lanza; ie, you could consider it a false flag. For all practical purposes, this hypothesis is a conspiracy theory. Yet it does not need to deny any victim. Indeed, one of the arguments for a false flag is that a lone shooter by the very noize gives warning to everyone else in the building, with which comes a chance to hide or try to run. More victims will strengthen, rather than weaken, this argument, albeit circumstantially.

Your digging is good enough to ascertain that the quote looks spurios. But you can still believe there were real victims but that the attack itself is a conspiracy.