It's wrong to give people false hope in a relationship.
Haley is in a relationship with Justin, and he has been hinting at wanting to move in together but Haley has been unhappy with Justin lately.
Haley doesn't want to hurt Justin.
Haley tells Justin that their relationship was no longer working and that she doesn't want to waste his time any more than she already has.
Haley gives Justin non-commital answers about moving in together and makes it sound like she seriously thinking about it.
Justin is upset but is able to move on and find someone who he is more compatible with.
Justin eventually grows frustrated with Haley's indecisiveness, and they have a huge fight.