It could be that she got caught in a situation where she couldn't find a restroom in time. For example, the restrooms at the prom venue were too far away or there was a long queue. Another possibility is that she had some sort of medical issue that she wasn't aware of, like a urinary tract infection that made it difficult for her to control her bladder.
Maybe she drank too much water or other beverages before the prom and couldn't hold it any longer. Or she might have been really nervous which affected her bladder control.
She could try to find a private place to clean up as much as possible. Maybe ask a close friend to help her find a quiet corner or an unoccupied room.
For fun. Sometimes siblings just like to do silly things together and dressing up in unexpected ways can be a source of laughter.
Maybe for creativity. Moms often like to be creative with their kids' looks.
It could also be that the mom is trying to teach her son about gender fluidity or break gender stereotypes. By dressing him as a girl, she is showing that there are no strict rules about what boys and girls can wear. In some cases, it might be a form of art or creative expression within the family.
One reason could be for fun. The mom might think it's a humorous and light - hearted way to make prom more interesting for the child.
Maybe she had a medical issue like a bladder problem. It could also be that she was in a situation where she couldn't get to a toilet in time, perhaps she was in a very long line or lost in an unfamiliar place.
One reason could be for fun or a special occasion like a costume party. Maybe the mom wants to see how cute her son would look in girl's clothes just for a laugh.
One reason could be for fun. Maybe they were bored and wanted to do something different and hilarious. Another reason might be for a prank. She could be planning to surprise their friends or family in a funny way. Also, it could be a form of self - expression for the girlfriend. She might be into fashion and makeup and wanted to see how her boyfriend would look with a feminine makeover.
One reason could be for fun. Maybe the mom has a great sense of humor and thought it would be a hilarious idea to see her son in girl's clothes. Another reason might be for a special occasion like a costume party. If the theme is something like 'dress as the opposite gender', she would dress her son as a girl.
It could be that she misses having a daughter. So, dressing her son as a girl gives her a chance to experience some of the things she might have done if she had a girl, like dressing up in cute girlish outfits.