Hanastrew, Eileen's protege who takes over leading the fairy squad after the infamous defection, and Melanbury, L'Evallier's equally posh and noble wife, are good friends too. This is despite the fact Melanbury loves healthy eating and eats loads of salads. Hanastrew considers salads to be no better than rabbit food and feels you can't beat a decent slice of chocolate cake. In fairness Hanastrew is kept so busy tackling the realm's nastier magical creatures she easily burns off every bit of cake she ever eats. Melanbury is a little fascinated by Hanastrew's derring do attitude. Hanastrew sees Melanbury is generally kindly (not something that could be said of every elf) and wants to break free from her traditional posh girl role of getting on with breeding heirs and at least have some kind of career first. Hanastrew sympathizes with that.
The most damaging "friendship/rivalry" is between Stanrock (imp) and Whespy (pixie) and even they don't know whether their relationship is more good or bad. They do urge each other into scrapes though and have managed to annoy every member of the Royal Household, which is a feat only they are proud of, and only they seem to be taken by surprise when they are exiled to Earth. For the Kingdom it came as a relief. In the realm's view friendships are not always a good thing.