So the general consensus is that Hailey is presently too selfish to be able to enter a relationship in a healthy way, and I agree! I've got a lot of season 1 Anne Boonchuy vibes from her. She has this sort of skewed image of friendship.
And in Hailey's case, it seems reasonable that she would. Her best friend and only real friend has only ever been Scott, who is very much just this sort of yes man in her life, always sort of going along with her. We do see him start to challenge this in a few of the episodes, as well as Hailey make efforts to rectify the behavior. She is definitely growing! But she clearly struggles to understand that others are not like Scott. They won't just go with her flow because she wants them to, and they can't be easily manipulated like him.
Another thing to consider is that she is only 14. If someone claiming to be from the future burst out of my closet when I was 14, telling me the entire world was going to succumb to a fiery apocalypse unless I alone reversed global warming, I honestly probably would've just laid down in traffic.
It isn't exactly right, but I think it totally makes sense for Hailey to be as self-centered as she is right now. She has to save the world and the ONLY person that she can share that with right now is Scott. And to be honest, though he is more than happy to help her wherever he can, he probably isn't very great for the more in depth emotional support someone in that situation might need.
We aren't even one full season in, and the characters have so much room for growth!