That's a very ingenious suggestion, and there's a sense in which your 'clean slate' suggestion is true. (More about this in a minute.) But I think you're really overthinking this.
The fact is, in actual conversation people don't pay a lot of attention to the formal alignment of verbforms and verb constructions. They don't have to. Context is at least as important as actual words and syntax in decoding meaning, so your hearers will ordinarily hear what you mean rather than what you say. And in speech, if ambiguity is strong enough to produce real confusion, your hearers have the opportunity to rewind the conversation and seek clarification.
So the fairly strict rules which operate in written texts aren't necessary in speech: a speaker is free to shift temporal and modal perspective almost at will. And I think that's what's going on here. The Rugrats writers (who are very good at their job) put themselves in Charlotte's skin and produce dialogue that reflects the flow of her consciousness, unconstrained by formal syntax. Annoyed by Angelica's whining, she invites Angelica to contemplate the possibility of having what she wants—and then shoots her down by pointing out, as a certain, non-contingent fact, that in two weeks Angelica won't care.
That's how real people talk.
The lesson to be drawn from this is that actual conversation, and even highly crafted fictional conversation, is not a useful source for understanding English grammar. English grammar is sort of like traffic laws, only strictly followed when you feel like the police may be watching; at other times, speakers and drivers feel free to transgress within their personal risk tolerances.