As has been mentioned above, admissions in previous years are irrelevant to this particular year, and using examples in an appeal would be a waste of time. Look at this year, and as dzug has mentioned, try to find out if any children without older siblings at the school or statements of special need, who live further away, have been admitted.
As regards the appeal, it would need to show very strong reasons as to why the child would benefit educationally from attending that particular school. Letters from current teachers and medical professionals would be a huge boost. I would imagine that the intention to move into the area would hold very little weight, but difficulties with transportation would be considered. I am aware of 2 families in my area who successfully won appeals - one had a letter from their child's paediatrician to say her social development would be severely impaired if she were split from her group of friends, another was successful at appeal because she was able demonstrate that she could not physically get her daughter to school on time because her son attended a distant school.
You friend needs to think very carefully about whether she wants to subject her family to a stressful appeals process, and a period of great uncertainty. If the school is very popular, you can be sure that there are many other families gearing up for an appeal too.