She should enter 12th grade into STARS and mark the classes as in progress. It’s covered in the FAQ on this page: STARS record Information - Admissions | University of Pittsburgh
How do I list my senior classes on the STARS record?
We encourage you to apply early, so senior courses should be listed but appear as “In Progress.”What if my senior schedule changes after I have submitted the application and STARS record?
You can go to the STARS record and resubmit it for your scheduled changes to be reflected.