I have made a queen quilt for a king sized bed. When there is a bed skirt on the bed, it is okay if the quilt only goes just past the top mattress, because the skirt takes over the rest of the sides of the bed. If you made a queen size, I am willing to bet your friend will find a great use for it, even if they don't use it on the bed.
That said, a quilted throw or lap quits for both are a fantastic idea!