I believe you are right on track with your protocol for your VolleyPSA. I would say that you will need to start looking at possible unofficial visit destinations soon, because she needs the opportunity to get on campus to 'feel' the different opportunities. What you want to avoid is just taking one visit, and using just this one experience as a touchstone. Your PSA may have a great visit to a school, and think nothing can compare.....but, she needs to visit a few schools to be sure.
It is absolutely reasonable to express to potential schools her timeline because this is her volleyball playing experience and not theirs. What I suggest is that you/her sit down and put together a list of schools pre-Qualifiers which 'sound' attractive to her. Nothing ranked, no top this or that, but rather just those schools which she would like to know more about.
Then encourage her to 'explore' these schools on line, to read about the volleyball programs - This is an easy way for her to start engaging in the process of winnowing down her list of potentials. As for the emails, please let her know that she should be more concerned about 'reading' them and not 'responding' to them. A simple, "Thanks for your email and information. As this is a busy time, I am focusing on school and practice. I appreciate your interest in me."
She should only be responding to those schools which have made her general interest list - If a school emails her which she has no interest in (for whatever reason), she can either hit the delete button or just let them know "that your school is not top group and please be kind enough to remove me from your recruiting efforts". This is a business, and I guarantee you that if she did not meet their needs, the college program would just hit the delete button on her.