Well, I'm the oldest in a family of 3 (kids) And if your younger sibling is being very dramatic I find there is a couple of ways to fix this.
One: Sit down and tell a story
Two: Intertain her with toys
Three: FOOD
Four: A movie
Ps I understand how it is, just don't stand down and let her know you she is getting to you.
please mark branilest:)