What Would Helga Do if Arnold Were Gay?
What would Helga do if hypothetically Arnold realized that he was gay?
Even though Helga is a 9 year old child it's established that Helga is very emotionally mature & intelligent, so even though she's young I can't see her being foolish enough into thinking that she could "change" him into being straight (but I could admittedly be wrong as Helga's done lots of crazy things before). I see Helga still wanting Arnold in her life even though it can't be in a romantic way anymore. Her romantic feelings for him would definitely be a struggle for her to get over, but I just can't see Helga not wanting Arnold to be an extremely close part of her personal life, even if it's just as a really close platonic friend. The two sorta, kinda, already have a close platonic friendship (or at least the foundation for one anyway) as Arnold is one of the very few people that Helga actually feels comfortable in sharing & confiding her personal home life problems in.
For those people who have seen the show "Dawson's Creek" I can see the friendship between Helga and Arnold (if he was gay) similar to the characters Jen and Jack's friendship from that show. Jen and Jack are soul mates in the truest sense of those words, only platonically rather than romantically, and Helga and Arnold could be something like that.