It used to be quite difficult to claim and you had to jump through lots of hoops but ever since last September it has been made a lot easier. As long as she got a good at her last inspection she should be able to claim. Where you live makes no difference, she will be paid by the LA where she works.
Each LA pays a different rate, in my area (Surrey) it is £4.15 an hour. She will not be allowed to charge a top up for the 15 hours, they have to be completely free, but she can charge you more for the other hours.
So, you currently pay:
£8/hour x 30 hours per week = £240/week.
Just for arguments sake lets assume her LA pays £4/hour:
£4/hour x 15 funded hours = £60/week.
£240 (what you pay now) - £60 (funding) = £180
Dividing that by the remaining 15 hours gives:
£180 / 15 non-funded hours = £12/hour.
So she could change your contract so that you get 15 hours free and another 15 hours at £12/hour. That way you benefit from the funding and she does not lose out on her income. This is how I have been instructed to do it by my LA and it is all perfectly within the rules.
I started claiming last year and the process was very straightforward. Just a few short forms to fill in. If she gets started on it now she should be up and running for the term after Easter. She will most likely have missed the deadlines for this term already.