Your little sister, who is 14 years old, has been extremely emotional lately. her mood changes very abruptly. although at this point there are many changes that are taking place in her life, and her emotions seem to reflect this, what is likely to occur as she develops into late adolescence

The answer is "her emotional states will become more negative".

Outrage, disappointment, fear, and other "negative emotions" are all piece of the human experience. They would all be able to prompt pressure and are frequently observed as emotions to be maintained a strategic distance from, disregarded, or in different ways repudiated, yet they can really be solid for us to understanding also. A superior approach is to oversee them without denying them, and there are a few purposes behind this.

She is going through puberty.

Read the American Girl books, they are great!