If it were me, I would definately speak to your supervisor, and explain to her just what you have shared here. Assure her that it is nothing "personal" against the other preceptor... just that you are not able to learn as well as you feel you could and should be under her watch.
Hey, this is YOUR learning time... take advantage of every GOOD thing if at all possible. If that means the other two preceptors, then by all means request that the remainder of your time be spent with them. The goal is to learn and grow and improve your skills and thought processes. This is the time to do it, before you are on your own.
I understand fully the not being able to learn from a "jittery" type personality. I couldn't, either, not that it makes that person a bad person... I DO understand where you're coming from. So don't feel bad.
Right now, you've got to get ALL YOU CAN, WHILE YOU CAN ! Choose what's most conducive to meeting your learning and growing needs at this time. and for what time is left.
Wish you the very best.