Study Student and Literacy

I have been seeing unusual behavior from my study student lately. It seems that her reading fluency is getting worse as the year goes on. My C.T. has noticed this as well, and is not sure what exactly is causing it. The student might be held back this year so that she can improve her literacy skills. I do not know what the right choice would be, but as of now she loves school and is one of the students who actually does all of their work. I find her reading books for outside of class during free time, and taking an interest in reading and writing. So I wonder how is it that her reading skills seem to be getting worse? Have any of you had any experiences like this?