You can do as many PIs, MIs and CPs as you get accepted for but you can only do 1 consecutive year if the internships at a time. Once you have done a full year you have to go back to shook for a semester before you can apply again.
Also it is a mix and match type situation so you can do a CP and PI back to back or PI an MI back to back or two CPs and all would equal one year and you would have to take the semester in between trying again.
So if she extended her CP then goes back to shook for the semester it is best to try for PIs and MIs before reapply for a CP.