Yo, so I just got the everyone ending. Basically you just follow through Landlord's route (as I think you did + the other requirements). Eventually he'll give you Britannia's pic, then you just gotta keep taking a walk until you find her (for me it was during the afternoon), from then you can tempt her going to the island. (Hope this helps, and also hope it isn't all that confusing to read, I'm really lazy -,-)