I wouldn't call Momo a trash character.
The thing is, she's never really had the emotional maturity that she projects. Each AnthroPC serves as a foil for their human companion and not always "other side of the coin" kind of a foil. Take Marten and Pintsize for example. For the most part, Marten is a decent guy who does have some trouble connecting to people, whereas Pintsize is an unapologetic little arsehole who prods and pushes the limit of what people will tolerate from him. But at the end of the day, Pintsize's intentions are good, he knows that Marten needed a push and in doing so, kickstarted his circle of friends. Its just in Pintsize's mind, you can more flies with crap than you do with honey.
If you look at Marigold and Momo, you can see the friendship between them, after all, Marigold valued Momo as a person enough to purchase a new chassis. The problem I imagine is that an AnthroPC is meant more to strengthen a person's weaknesses, to bouy them in the areas lacking in their lives and to be honest, I didn't really see Momo do that compared to the other AnthroPCs (I fully admit that I might be wrong here).
The thing is, the world according to Momo should be Black and White, following a set of rules that anyone can understand. So it's difficult for her to understand how or why someone can step out of that box (the initial phases of her friendship with May, her disagreement with Bubbles' having served in the military). And she's been repeatedly shown that its not.
I imagine that this storyline is less about May and Sven connecting the USB port and more about Momo having to undergo some form of emotional and mental maturity. I mean, right there in the comic, she said she was attracted to Sven, in essence calling dibs. And yet, she never acted on that attraction or even worked up the courage to speak to him. Momo might feel upset, but the fact is that you don't get anything sitting around twiddling your thumbs and you can't lay claim to people.