If you are only claiming your portion, only include yours.
However, in my opinion, if your mom never lived there, I would claim the entire portion of rent (both halves). If the state questions it, you can just explain that you were the ONLY one that lived there, despite somebody else being listed on the lease. You could point out that the instructions show that a roommate who is NOT on the lease should be separate out on a separate CRP - meaning that the CRP and the credit is based on the actual number of people living there, NOT on who is listed on the lease.
