A friendship can weather most things and thrive in thin soil but it needs a little mulch of letters and phone calls and small silly presents every so often - just to save it from drying out completely.
Sisters are always drying their hair. Locked into rooms alone they pose at the mirror shoulders bare trying this way and that their hair or fly importunate down the stair to answer the telephone.
Suspense is very important. Even though this is humor and they're short stories that theory of building suspense is still there.