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.
One way could be to write something like 'The girl's stomach let out a low growl, like a tiny beast awakening inside her.'
Once there was a girl named Lily. She was in a very important meeting at school. All of a sudden, her stomach growled really loudly. Everyone in the room turned to look at her. She blushed bright red. It was because she had skipped breakfast that morning. She was so embarrassed but then she just decided to laugh it off and told everyone she was really hungry.
Once upon a time, there was a girl named Lily. She was in the middle of a very important meeting. Suddenly, her stomach growled loudly. Everyone in the room stared at her. She blushed deeply and tried to come up with an excuse. She said that she had a very hungry pet mouse in her pocket, which made everyone laugh.
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.
Well, stomach growls in manga can be used for humor or to emphasize a character's situation. Like when they haven't eaten for a while and it shows their need for food. It can also be a way to build tension or add a bit of randomness to the story.
Stomach growls happen when your stomach is empty and it's trying to tell you it needs food. In comics, they might show it with wavy lines or a rumbling sound effect.
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.
One possible reason could be the power of imagination. Fanfic often creates vivid and detailed scenarios that can stimulate a girl's imagination in a sexual way. It might allow her to explore her sexual fantasies in a somewhat safe and private environment.
One reason could be to create a unique love story. Writers like to take unexpected pairings to make their fanfics stand out.
Maybe she ate something bad like spoiled food or food she was allergic to.