Sustainable Development. Under the Scottish system, you can take modules from other subjects in first two years so can incorporate her interest in philosophy, music and human geography. Not sure, if it applies to Edinburgh, but St Andrews have the same system and you can change your final degree as long as you've taken modules in that subject in the early years.
As with Laniakea's DD the only thing not linked to the course was the mention of her music scholarship which showed she can manage her time well with many commitments.