No, Suselle isn't doomed.
Please read this all the way through, I'm trying to approach this objectively and from a writing and character standpoint.
And this is no hate to other ships... I've been critical of them before on this sub but legitimately I've walked it back. I could see the other ships being very compelling in another story, which I think is a massive compliment to Toby Fox's character writing.
I've noticed in the fandom that there's this theory / belief / general feeling held by some people that Suselle isn't going to work out.
And I understand where it comes from, the pacing of their relationship especially with chapter 5 was a weak point in the story. That combined with the fact they are a simple and happy couple, has lead some people I feel like they're "too good to be true". Like Toby Fox is gonna pull the rug out from under them.
But the pacing really is the only problem. How much you enjoy seeing them together is personal and subjective, but their chemistry is strong and their love for eachother is believable even though it's at its earliest stage.
I do think they could've used more time just around eachother casually to build up to the lake scene, for writing quality purposes, but that doesn't make their relationship suspicious in canon. For that to be the case, everything Noelle and Susie said to eachother in that scene would have to have been a lie, or their strong and real feelings would have to be shattered.
And I DO believe their relationship will be tested, I HOPE it will be... Like, if Noelle ends up making a dark world, potentially becoming a full on temporary antagonist, that could definitely cause issues between them. I can see them fighting, I can see Susie being angry and feeling betrayed.
But unless one of them acts COMPLETELY out of character, it would be equally out of character for the other to have their feelings for the other IRRECOVERABLY damaged. Susie would feel betrayed if Noelle, say, went "team knight" or something. But if it was because she wanted to save her DYING FATHER, I think Susie would be understanding.
I could see Noelle make a dark world, work with the knight, blah blah blah XYZ for Rudy related reasons or potentially even Dess related reasons.
I really cannot imagine, though, a compelling way for the final result of this to be Susie saying "Wow Noelle you're a traitor, I don't wanna be your girlfriend anymore."
"I hate you so much because of this that I'm changing my mind about when I said being with you was the happiest day of my life, and how I said I wanted to make your life happy in contrast to the crushing depression that has previously defined your life, which I can relate to."