Those are both concerns I had after the gig I went to when talking about her Glastonbury headline potential. The middle filler bit can be dealt with by doing slightly less of the slower songs and replacing them with a guest.
Very little can be done about the fan thing though, so it'll be different in terms of crowd reaction. Will be interesting to see how it goes
I Did not see her last time - but all i remember from last time she played was that anyone who was there were talking about it as one of the best things they have ever seen. I don't thin she needs to worry too much about not having her legions of fans there at all to be honest.
I would not stress too much if you don't like her - Glastonbury is never short of other options