|Nikki's Unknown Sister|
|Published by||Xilbris Publishing|
|The Grass is Always Pinker||Exam Trouble|
Nikki's Unknown Sister is 13th book in the All About Us series.
Nikki is featured on the book cover, along with her sister, Sarah.
Nikki catches her father hooking up with an old flame and learns the real reason why her parents split up in the first place. She is shocked to learn the existence of an unknown half-sister.
- Nikki's parents split up in the last arc.
- Sierra mentions her parents' split, which took place in the All About Middle School series.
- Nikki is wearing a pink over-the-shoulder sweater, black skinny jeans, Military boots, studded bracelet, and a cross-body bag.
- Nikki learns that she has an sister.
- The first appearance of Sarah Giuliani.
- Nikki's Unknown Sister/Spoilers, spoilers from the episode.