Ruby is one of the current side-characters, and is part of the student council. Ruby is one of two students in the cast that doesn't have any Celestial Magic whatsoever - she's just a regular human that attends a school filled with magic. She makes more of an antagonistic appearance later on in the series, however for now she's just a side-character. 

Ruby's voice is fairly high and she's also very emotional, which is why she comes on later as a villain. Her voice is a bit annoying, but confident enough that it's gotten her into the student council.