In the Umbrella Academy comics, Vanya's character is indeed gay. This aspect of her identity is an important part of the story and character development.
The Sparrow Academy is not a part of the original comic storyline. The TV show introduced this element to add new twists and developments to the story.
In Umbrella Academy fanfiction when Vanya is blamed, it can add a lot of depth to the story. Her character is already complex in the original series. Fanfic writers may use the blaming aspect to show her isolation and struggle. Maybe they have her face more unjust treatment from her siblings or other characters. This can lead to interesting character development as she either tries to prove herself or becomes more withdrawn. It also allows for exploration of themes like prejudice and misunderstanding within the context of the Umbrella Academy universe.