I am a middle school band director. Maybe I can help.
Your director should be able to help your student find the instrument that is right for her. I do not pick percussionists until later in the year as well. There's lots of reasons, but trust me, as a percussionist myself it is the worse instrument to start on. I only allow beginners to start on Flute, Clarinet, Alto Sax, Trumpet and Trombone. Those instruments set the students up for success. Later I'll choose students to have the opportunity to play Tuba, Percussion, French Horn, Euphonium, and percussion. I hand select those students who I feel will be able to handle the responsibility and have the work ethic to play those instruments. DO NOT start on oboe or french horn...terribly difficult instruments...not for beginners!!
I recommend renting the instrument as well.
BTW, If more than half of the first year band students do not sign up for band the second year that's a red flag to me. Something doesn't sound right about that.
Good luck, PM me if you have more questions.