I'm not sure specifically about non - adult fanfic related to Melissa O'Neil. You could try searching on fanfic - dedicated websites like Archive of Our Own, where there might be various types of stories about her that are within the bounds of appropriate content.
You can start by looking on fanfic platforms such as Wattpad. Some fans might write positive stories about her there. Also, check out any official fan forums related to the works she has been in. Fans often share their creative works in such places.
I'm not entirely sure which specific 'April O'Neil' this refers to. It could be from the Teenage Mutant Ninja Turtles franchise. If so, fanfiction about her might explore her character in different ways, like her adventures as a reporter, her relationships with the turtles, and how she copes with the strange world she's a part of.
One idea could be to write a fanfic where April goes undercover in a dangerous organization. She could use her reporting skills to gather information while trying not to blow her cover.
Definitely not. The idea of basing a fanfic around something as unseemly as flatulence in relation to a character like April O'Neil is inappropriate. Fanfics should usually enhance or explore more positive aspects of a character's personality or the world they exist in, not involve such crude ideas.
One characteristic could be its exploration of future technologies. O'Neil science fiction often presents advanced concepts like space habitats and new forms of energy. It might also focus on the social implications of these technological advancements, such as how they change human relationships and societies.