No. Fanfiction should focus on positive, respectful and appropriate content. Lesbian sex fanfic often involves sexual content which is not suitable for public consumption and may violate ethical and moral standards.
Well, it's not appropriate. Fanfic is supposed to be a creative exploration within the boundaries of good taste. This kind of content that involves sexual themes, especially in a workplace - themed context like 'the office', can make people uncomfortable and is not in line with the general norms of acceptable literature. It can also be offensive to some people in the LGBT+ community who want positive, non - sexualized representation.