Agnes vs. Agnus

When she is doing her math homework, Agnes has written her name at the top of the page. Only she wrote 'Agnus' instead of 'Agnes.' When I first noticed it I thought it was a nice touch; like, 'Wow, this girl is living in such a messed up environment that she can't even spell her own name.' But as the movie went on I realized she's supposed to be extremely start and a really good writer and that particular page of math is, uh, calculus, even though she's only fourteen. So she's pretty much a genius yet she misspelled her own name. So I'm treating it as a goof until someone explains why she would have done that.