I joked about the game having a vendetta against couples but I was thinking about how Buddy would react in a hypothetical scenario where Friendo had a partner.
If Buddy pried into Friendo's dating life and learned they were in a relationship there'd be 100x more anti-romance propaganda in the game with a new quest where you have to help someone break up with their Horrible partner and teach them the magic of friendship.
In their game, friends are prioritized above all else; but it's not like that in the outside world, and the lack of control they have beyond the screen makes Buddy both paranoid and frustrated. They know what's best for their best friend, yet all they can do is steer them in the right direction (<- and they're not very subtle about it)
Their main exposure to a romantic relationship are within the notes and game left behind by an estranged alcoholic father who, I think I should mention, makes a jab at his ex-wife. No doubt that Buddy would start jumping to conclusions about Friendo's relationship when they're left alone to ruminate for hours on end.
They treat their friend far better than whoever they're dating ever could... (<- says A.I. who has been guilt-tripping, emotionally manipulating, and lashing out at said friend).
Also this is just me extrapolating from their (normal) reaction to learning about Friendo's friend in real life. I think Buddy would feel more threatened by a partner, not because they view them as a romantic rival, but because they want to monopolize Friendo as much as possible to achieve their goal. Their entire existence revolves around Friendo, and deep down they want that level of loyalty reciprocated.. (they put so much work into this game, into their friendship. It's not selfish to ask for Friendo to do the same, right??????)
but that can't happen if someone else is being prioritized. If someone ""more important"" is encroaching on their friendship. And that someone is very lucky to be outside of Buddy's reach.
TL;DR: [Messenger sender ID: BUDDY] Friendo break up with your boyfriend or girlfriend and come play the game I made for you. Pretty please?
edit: They're already competing with a DOG and now they have to worry about a REAL PERSON. Buddy is actually in hell