Leave isnt actually allocated on first come first serve, its down to seniority and unfortunately as your daughter is so new to the company she is not as likely to get the leave she has requested if its a popular time to take it. As there are so many crew above her in seniority.
Unfortunately many other new crew will be in the same situation and i'm afraid it is a case of waiting to find out. This will only be because she is in her probation though. For the 2nd half of the year she will be able bid and get her allocation at the same time as everyone else. On the other hand if she doesnt find out untill may, then that will surely mean that the only month left for her leave to be given will be in june, as she has to take her leave owed to her before the 2nd half of the year.
One of the downsides of this job is that nothing is guarenteed and its never a good idea to book or pay a deposit untill you have it in writing.