A girl may have a pale white stomach if she is constantly stressed. Stress can affect the body's hormonal balance and blood flow, which may lead to paler skin. Also, if she has a genetic predisposition to having fair skin in that area, it will be pale white. Moreover, if she recently recovered from an illness, especially one that affected her digestive system, her stomach might look paler as the body is still in the process of fully recovering and getting back to normal blood flow and pigmentation in that area.
Once upon a time, there was a girl named Lily. She was very fair - skinned and her stomach was a pale white. One day, she was going to the beach with her friends. She wore a cute bikini, and her pale white stomach was exposed to the sun for the first time in a long while. Her friends joked that she looked like a porcelain doll. She laughed it off and they all had a great day playing beach volleyball and swimming.
Another possibility is that she has some sort of stomach ailment in the context of the fanfic. Maybe she ate something bad earlier and now her stomach is protesting. Or perhaps she has a condition that causes her stomach to make noises at unexpected times, which can add an interesting plot twist to the fanfic as other characters might react to it in different ways.
A possible reason could be a curse. In fanfiction, a character might be cursed, and as a result, their skin turns pale. This curse could be related to a past misdeed or an ancient power that has been awakened in the wrong way.
Maybe she ate something bad like spoiled food or food she was allergic to.
Racism could be a major reason. If the white boy was being racist towards the black girl, she might have fought back. For example, using racial slurs or treating her as inferior.
One reason could be that she's been really busy and hasn't had time to eat. For example, if she's a student cramming for exams all day long, she might forget to eat and her stomach would growl as a result.
Food is a common reason. For example, if she ate beans, which are known to cause gas, along with some spoiled food, it could lead to both stomach ache and farting. Maybe she had a meal at a roadside stall where the hygiene wasn't so good.
It could be for the pursuit of freedom. Maybe Kara was holding the girl against her will in a restrictive environment. The girl, longing for freedom and a better life, decided to escape. For example, if Kara was in charge of a strict and unfair orphanage where the girl lived, escaping would be a way to seek a more positive future.
Sometimes, it's a result of a planned diet change. Maybe the girl realizes she's too thin and wants to have a more curvaceous body. So, she starts consuming more calorie - dense foods like cheese, chocolate, and fatty meats. Or perhaps she's an athlete who has been training hard and now needs to gain weight for better performance. In this case, she'll focus on eating more protein - rich and high - calorie foods, which will lead to her fattening up in a healthy way.
Jealousy can be a reason. Just like in the story I mentioned before where two girls liked the same boy. Also, misunderstandings. For example, if one girl thought the other was talking bad about her behind her back when it was not true at all. Another reason could be competition, like competing for a role in a school play or a spot on a sports team.