Dataform (plugin)

We have students (Mentee's) who submit forms. They are linked to a Supervisor (Mentor). The Mentor role is a limited Teacher role. The Supervisor (Mentor) needs to check their students submitted form(s) and approve. The problem I am having is that Supervisors (Mentors) can see all student submissions, rather than just the student(s) they are linked to as Mentors. I have previously been able to successfully achieve what is required here with the Checklist plugin, but I can't seem to get the exclusivity required with Dataform. If I set the Dataform to "Separate Participants" the Supervisors (Mentors) can't see any form submission (other than if they complete and submit their own form), and if I turn that setting off, they can see all student submissions.  I considered using group entries, but it would mean setting up hundreds of small groups, and the linking is already done anyway with the Mentor/Mentee function. Anyone have an idea on how to achieve this. I'm sure it can be done, but everything I've tried does not seem to work.