In some children's books, there might be such stories in a very innocent way. For example, in a story about a group of kids on an adventure, a girl character might accidentally fart while they are hiding from a 'monster' which adds a bit of humor to the situation. It's not a main plot usually but a funny little side event.
One common theme is embarrassment. For example, a girl farts in front of her crush and is extremely mortified. Another theme could be surprise, like when a girl who is usually very proper and ladylike suddenly farts loudly in a quiet place. There's also the theme of humor, where the situation around the fart is made to be funny, such as a girl's fart sounding like a strange animal noise.
Well, there was a girl in my class. Once during a really quiet study session in the library, she accidentally let out a little fart. Her face turned bright red and she was so embarrassed. But then we all just kind of laughed it off and it became a funny memory among us.
Well, one story could be that a girl ate too much junk food at a party. She started having a stomach ache later. As her stomach was in discomfort, she couldn't hold in a fart. It was really embarrassing for her, especially when she was around her friends.
Well, I know of a story where two girl friends were sharing a small tent while camping. In the middle of the night, one of them farted really loudly which woke the other one up. They both ended up laughing so hard that they couldn't go back to sleep for a while.
There could also be a theme of acceptance. If the girl is in a group of friends who are understanding and accepting, the incident of squatting and farting might be quickly laughed off and not made into a big deal. Or if she's in a family setting, her family might just shrug it off as a normal, if a bit funny, occurrence.
A girl was playing a game of charades with her family. She got really excited and while trying to act out a word, she accidentally made a farting sound right in her sister's face. Her sister was shocked at first but then they both started laughing uncontrollably. It was a bit embarrassing but also a very funny family memory now.
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.
Once my two girl friends were having a sleepover. One of them accidentally let out a really quiet but stinky fart while they were all huddled up watching a movie. They just started laughing uncontrollably and it became a running joke between them.
There was a young girl who was on a first date at a fancy restaurant. She was really nervous. She accidentally swallowed a lot of air while talking. Later, she let out a series of small farts. She was horrified. But her date was really kind. He said 'Don't worry, it's normal. I'm just glad we can be comfortable around each other'. This made the girl feel a lot more at ease.