Souinds like someone doesnt know what they are talking about. DS was a baby when we applied for his and someone just allocated him an NI number - I can't remember (hes now 14) but I am pretty sure it was the DLA that got it for him.
But the DLA office should be able to access her details from her name and date of birth if you tell them you haven't got her NI number yet. However the people you speak to at DLA are a contact centre and can only go from what is on the system; so you may get more info if you ask them to get the person who is dealing with your claim to call you back (which may take a couple of days).
Applied for DLA for dd aged 3. Been 2 months now. All they asked me for was our dd and our nationality status. on phone the status is application is being waited to be looked upon. They keep asking for dd NI number. I called NI helpline for her number and they said they do not issue it to anyone less than 16 yrs old. When I told them about DLA claim, they said DLA people need to speak to child benefits team and sort it out amongst themselves. I am totally confused. it looks lame to me...am I missing something here?