I think Maya has just never been all that smart. Noriko seemed to outdo her in everything besides Japanese back during tutoring (possibly a reason she hates her):
And the tutoring itself seemed to be more of a cover up for her, since she apparently had nowhere else to go:
It seems like she was even staying where Sensei tutored:
Hence the beds, her showering, and her mentioning stuff like the blanket he got from a thrift store back then.
There's also how Ayane seems to casually outsmart Maya:
Albeit, Modern Maya does seem to have just wasted her intelligence:
And Ayane definitely seems to be one of the more intelligent girls in class. The top 3 likely being Nodoka, Noriko, and Makoto.