For the DLA, if you can get to your local jobcenter, go there and ask for the DLA form for a child. They will then date it and I think you get a month to return it for it to be backdated to the date you got the form.
It is available online, but better in the paper form and it is a bit of a nightmare of a form, rather intrusive, but it does sound like your dd would be entitled to benefits. How old is she?
There is a guide produced by cerebra which I found really helpful here It is aimed at children with brain related conditions but it gives you a good idea of how to fill in a successful application. If you pop on the special needs board on here too, people are always willing to help.
DLA is formed of two componants, a mobility payment and a care payment. Like your dd, my ds1 can't always walk because of pain, and he gets high rate mobility allowance, and middle rate care allowance. I don't think you can get the mobility until she is 3.
It is early days, but IME they do tend to not mention these things! Good luck with the appointment, and push for all the referrals you think will help.