@ceomommy21 - Can’t answer any specific questions about Gemstone, but as I understand it, students can always change to University Honors. Some of the other Honors Programs have limited space, so they may not be able to accept a new student.
My D started out with University Honors and completed the requirements for her Honors Citation by the end of Sophomore year.
The following link will let you determine credit your D can get for her AP courses.
http://www.transfercredit.umd.edu/plc/APGenEd.pdf
Graduation requires a total of 120 credits generally, split between GenEd courses and Required Major courses.
My D could have actually graduated in 3 years, with a heavy course load and AP credit., but she applied for a Departmental Honors Program at the end of her Sophomore year, which typically takes 2 years to complete.
If the 4 year Gemstone commitment is an issue, you should probably look into getting into one of the other programs, but first look at the 4 year plan for her major and the specific required course and see if a 3 year graduation is feasible.
Keep in mind that not all courses are offered every semester and there are prereq courses in certain majors.