I am on the appeal committee of my university and I endorse much of the advice that has been given by pp's.
-Your dd needs to take the advice of her SU advisors, they will have guided many students through the process before.
-Read any guidance on appeals and be very clear what grounds you are appealing on, these may be quite narrow and specific.
-Be very clear about all the regulations around borderline cases, in my bit of my university we round from 0.5 below the borderline and allow for special circumstances and that is it, so 58% would always remain as a 2.2 for us, no matter what the distribution of module marks. In other places this is different, they may consider either the overall distribution or the balance of 2nd and 3rd year marks.
-It is worth approaching your department for information and there is no harm in asking whether they took into account the concerns they had raised. You can ask to see the minutes of the exam board for that module, although this will be restricted (if they refuse you can make a Freedom of Information request). However there is probably little they can do at this stage so don't bombard them with demands.
-I have to warn that retrospective appeals for special consideration are usually refused here, unless there is good reason for not bringing things up formally before the results are out. Good reason is difficult to establish, thinking it wouldn't matter, ie expecting to get a better degree despite the problem, is not good reason. That's not to say that would be the same in all universities.
My concern here is the extent to which a group mark is being used in honours assessment, it would not happen where I am, in major group projects there is always a substantial individual part of the mark, to avoid the problem your dd now has. A poor group should not automatically mean a poor mark for everyone, that makes a substantial part of the degree classification down to luck. As an appeal committee we would probably discuss this and advise the department informally to reconsider this for the future. Unfortunately, though, I don't think the appeal would be upheld here.