As you and your sister have discovered, unfortunately none of the rooms fits neatly into just one map tile. That means that at least two adjoining tiles will need to be edited and merged together - since you say that the tiles containing the shed and the gate are affected presumably the mod is on the whole house and it looks like a large number of tiles will need to be edited.

There are a couple of tutorials on merging maps in the VF Mods forum and the discussion threads in the VF Mod Comments and Discussion forum might also give some help.