FPP changes

So if 1 fast pass has already been made for a certain day. Can you not go in and add your other two? Asking for a friend. I haven’t had to make any FPP yet so I’m clueless on how to help her add/change.

Correct, you cannot. You make all three at once. If you choose one of the options that gives you less than 3, or you cancel one or two of them, then you’re stuck with what you have left. Only option is to give it up and start over.