Which schools have you applied for? Appeals against the refusal of a place are specific to the individual school, so e.g. if you have applied to DGSG, TGS and Invicta and been told that there is no place available, then you must lodge a separate appeal against this decision for each of the schools and attend three separate hearings.
As your DD has been assessed as suitable for grammar school, then your appeal at each school where she has been refused a place will 'just' be looked at on the grounds of oversubscription- that is, the independent appeal panel will examine the school's case not to admit any further applicants and balance it against your case that your DD needs to go to that (specific) school.
In the meantime, your DD shoukd be on the waiting list for all the schools which were a higher preference than the one that you have been offered (check whether this is automatic, or has to be requested), and you should accept the place offered, unless you also have an independent school place as a backup or are geared up to provide a full year 7 curriculum through home education from September.
Also, how 'OOC for Kent' are you? And do you have to move to Kent? (big county, so whereabouts are your commitments if so?) Bearing in mind that most of the Kent grammar schools admit on the basis of an pass in the Kent Test, then by oversubscription criteria such as pupil premium / feeder primary school / sibling / distance, not by score ranking. This is not strictly relevant for the purposes of appeal, but moving close to a school which has distance, not score, as a main criterion would give you a better chance of a place coming up via the waiting list- plus you might have a hard time convincing an appeal panel that your DD has a pressing 'need' for a place at a school in an area where you don't currently live and have no particular need to move to (a place at a Canterbury school, because both parents have secured senior medical positions at the Kent and Canterbury Hospital and need to live close by for on-call commitments, for example)
Then admissions policies for all Kent Secondary schools are on the Kent CC website.