Well, the plot could involve the female Kyuubi being overly possessive of Naruto. Maybe she tries to keep him away from his friends and training, seeing them as threats to her relationship with Naruto. She might use her powers to intimidate anyone who gets too close to Naruto.
One possibility is that the female Kyuubi in the fanfiction has fallen in love with Naruto in a very extreme way. So she starts to manipulate situations around Naruto. For example, she could make it seem like Naruto's enemies are much stronger than they actually are so that Naruto has to rely more on her for protection, all while her yandere tendencies grow.
In this type of fanfiction, the plot could also revolve around Naruto being initially unaware of the female Kyuubi's yandere nature. As the story progresses, he starts to notice her strange behavior, like how she always wants to be with him and gets extremely jealous when he even looks at another girl. This could lead to a conflict between Naruto's sense of freedom and the Kyuubi's possessiveness.
A practical answer is Chapter 64, because it turns the idea into a concrete scene. The chapter opens with Chixia Village lay in tranquil slumber., adds pressure through Is there really a need to put her down like this?, and ends on He'd been a host for so many years; he was used to it..
A practical answer is Chapter 34, because it turns the idea into a concrete scene. The chapter opens with Seeing that the public sentiment wasn't quite right, Su Yinwan felt..., adds pressure through Hurry up and start the live show, I can't wait to watch the universe's..., and ends on Now that.
If you want the clearest chapter reference, go to Chapter 62. Early on, Sitting on the edge of her bed, she pondered for a while before lifting...; later, the chapter leans on The moment the door opened, she saw her photographer with his hand still....
A practical answer is Chapter 39, because it turns the idea into a concrete scene. The chapter opens with Qi Tianyu had been looking forward to watching Jiang Li's drama unfold., adds pressure through It's not by some great master, I copied it myself., and ends on His original intention was just.
Look to Chapter 40 for the clearest answer. It begins with [Jiang Li claims she copied this herself?, keeps building through But her calligraphy is actually this pretty?] [Jiang Li dares to boast,..., and lands on The handsome guys on this show are so difficult to deal with..
The best chapter pointer here is Chapter 14, "She Looks So Cool Dancing with a Gun". It opens with Lin Manru had a rare good night's sleep. and closes on But clearly, Lin Manru was unable to accept that her delicate daughter had....
A practical answer is Chapter 84, because it turns the idea into a concrete scene. The chapter opens with When the villagers tasted his curry beef one by one, their faces revealed..., adds pressure through [Pfft, and she's teaching others how to cook, isn't it just scrambled eggs..., and ends on.
A practical answer is Chapter 43, because it turns the idea into a concrete scene. The chapter opens with The moment He Yun willingly sat next to Jiang Li and even took off his..., adds pressure through VIP lounges and business class still count as transformation?, and ends on Just as she turned.
Look to Chapter 31 for the clearest answer. It begins with Before Shen Lan had reached the backyard, she already heard the sounds of..., keeps building through Facing the freshly risen morning sun, she noticed at a glance the girl..., and lands on After staying in the study and reading for another.
Chapter 82 is the strongest chapter-level answer because it starts from Jiang Li gave her a fleeting glance. and follows through on And so, aside from Wen Jiaojiao, the remaining five set off, each....