As I understand it, you get one credit for any booking, and if it is a suite it counts for two credits. A cruise of 12 days or longer earns another credit. No one can get more than 3 credits per cruise. If your daughter has 4 cruises with RCCL she will get credit for a fifth cruise and move to platinum level when the cruise is finished. I don't think she gets two credits unless she is a primary guest on the booking - but I could very well be wrong about that. We have some diamond and diamond plus members on the board and hopefully they will chime in here and either confirm what I said or correct it.
RCCL's Crown and Anchor rules can be confusing.