15. The girl with the long braids had to decide with whom she would share her popsiclehim or myself.
Rewrite:
15. The girl with the long braids had to decide with whom she would share her popsiclehim or me.
Why?
One must keep parallel structure here between two object forms of the pronoun after the dash with "him and me".
Note: the "whom" is OK because one must use the object case in the prepositional phrase "with whom".