The sprite is indeed probably lying, but you'd best make sure that she has no valid medical excuse that would require you to regrade her under school rules, if any such policies exist.
The policy now extant at my campus, where I am so glad to have worked hard to get it passed, is that students have 30 days to appeal final grades. Period. That has put an end to the ones who contact us again, a year after graduation, to say that they just realized that they can't get that job or get into that grad school or etcetera, and couldn't we just raise the grade a little? By then, I rarely remember them, as those tend to be the students who weren't around that much before they graduated. And that, of course, could explain a lot.