If you do get advice from the British Dyslexia Association, try to look at some of the things they reccommend for education and then see if the school you are appealing for sounds like it could fit some of those reccommendations. Look in the prospectus and OFSTED report for things the school does well that would benefit your dd and use it as evidence.
From my limited knowledge of appeals, which has only come from going through one in the same way as you, I think appeal panels do listen to things that aren't strictly relevant. For example, I stated during our hearing that I was concerned that my ds may be a target for bullying because of his social difficulties and a facial birthmark he has and that I was aware that the school we wanted has a strong bullying policy and a good reputation for dealing with it. In theory, all schools are supposed to have a good bullying policy, and deal with it equally well, so the appeal panel should possibly not have considered that as one of my many points. But on the letter we recieved today from the appeal clerk, it said that the panel had considered the fact that I was reassured by the school's good reputation for dealing with bullying. So the panel, while being proffessional, are human, and know that some schools are better than others at dealing with certain things.
So while I accept and agree with GiddyPickles point that schools deal with dyslexia daily (as they do bullying and aspergers - both very common) it can't hurt to raise your concerns. It's kind of obvious that some schools will be better at dealing with dyslexia than others.
In your situation I would also say that smaller class sizes for all pupils will benefit your dd because although smaller classes could be provided in a bigger school, that would mean segregating her and pointing her out to her peers as having a difficulty. Whereas if all students are automatically in small classes and recieve above average levels of attention, your dd would get the help she needs without making her appear 'different', which could damage her confidence and self esteem.
Again, I said something simelar to that, in that I said the high level of pastoral care and support was provided to all students in the school we were appealing for (and evidenced it from the prospectus and OFSTED report) which would mean that ds wouldn't need to be singled out for extra special support that would draw even more attention to his differences and difficulties. Again, it was mentioned in the letter explaining why we won the case, so I think the panel did take it into consideration.
You need to use absolutely everything you have, let the panel judge whether they think it is relevant or not.