A 4/29 sailing is now in full penalty. That means they keep everything except the Gvt taxes. It would be easier to get a second medical opinion than to get CCL to waive these fees. They sell insurance and to allow a waiver on the penalties would undermine thier insurance program. I have only once ever seen them waive the penalty and that was an error on one of their Res Agents part that after it was done they were stuck with. They have since reprogrammed their system to not allow the same error twice.
You need to quickly and in writing have them plead the case. You will recieve a written response but in this case perhaps too late. Call them and ask where you can send the correspondence via email so perhaps you can get their reply quickly.
One other option is to find someone else to go in her place. There will only be a $50. re-doccumentation fee for changing pax.