go to seahorse and buy a matress (foldable type) for your maid, At night she will sleep on floor beside your kid's bed with the matress. At daytime, put away the matress under the bed or elsewhere.
I think 2 1/2 feet is enough. I think your maid also choose sleep little space & 下格!Because if you put 4 feet bed in the daytime the room is very small. But if you put 2 1/ feet in the day time more space !!!!
I think your daughter is not a fat lady !!