Can you put Lily's food up somewhere? My first reaction was to say on a counter, but it's hard enough to keep kitties off counters that I wouldn't want to enourage it. But somewhere up where Luna might not be able to get it?

Other than that, sorry, but I have no suggestions. Maybe it's just a temporary thing though until the boundaries are firmly set between Luna and Lily and Luna doesn't feel like she has to gobble it all down before Lily gets it.