I feel like the best way to develop a plot is to ask many questions about it so here goes:

Does the rp have a certain goal in mind? Like why the borrowers are borrowing these things? Is there something they have to arrange (like a ceremony for one of them or a party maybe?) and why is it important? What happens if they are unsuccessful?
Oh and would either of the humans find out about the borrowers? Also would they be interested in the daughter despite her being not so nice? Perhaps one of the friendly borrowers could be curious about her problems and maybe try helping her indirectly.

 (Also,I think I should mention that I haven't seen the movie)