How does a full ride affect sibling aid?

Hi guys, sorry for the big confusion. So my sister goes to CMU, and we do qualify for aid. The thing is that CMU just didn’t give her any. We are definitely not a full-pay family, and we will not be able to afford two full-pays, we barely are living with one. The reason I was thinking half is because looking at my other financial aid offers for other schools I’ve have to pay around 40k on average, and because my sister has friends at CMU that are paying around half because they have a sibling in college. Also, my sister has not received her financial aid from CMU yet.