Sister and I's tablets RCA ones are not letting me join my worlds and her not go past white minecraft loading screen her username is kdcards and mine is Ldwhisp plz fix this

PLEASE FIX MY SISTERS AND MY MINECRAFT!!!She is stuck on the minecraft loading screen and I can't join my worlds or create new ones plz fix or we may just delete the app because we are having to many issues and problems. Please fix this is later updates. Thantablet.And sorry but my tablet type wasn't there so I just used kindle fire but it is a RCA tablet and it is on version 4.4.2
~Ldwhisp