Yes, if she's lying it would meet the definition of premediation in pretty much any state, since it obviously would have been planned at least several minutes in advance and even in states where premediation really means more than forming intent 2 seconds before the act it would still qualify. But I should mention that isn't relevant here since TX has one crime of murder, not two broken into degrees, and it doesn't require premeditation. Premeditation isn't needed to prove murder there. Only thing required is "malice" which is basically a wrongful intent to kill, meaning intent without justification like self-defense.
Something else I would point out here though. A jury could well end up believing her. Or not. Hard to say. On the one hand, her mistake story is perhaps hard to believe because, well, who makes that sort of mistake, right? Then again, OTOH, no motive for murder has been found. That's going to make it tough on the jury. I myself am still not certain if this was murder or manslaughter. The only thing I'm certain of is that she's guilty of one or the other.