The 25-year-old star - who called time her relationship with the model in July after allegedly discovering he had cheated on her - claims she and Luke both knew they weren't happy in the relationship, but there is still a small part of her that really wants to be with him.
She said: "It's been the hardest thing I've ever had to deal with in a long time, and I'm not over it. And for a while I thought a small part of me wanted to still be with him, but it's not right.
"The best your relationship is ever going to be is how it is when you're dating. We weren't happy anymore. I had to go to the next step in my life, and so did he, unfortunately.
"It sucked way more because I was going to marry him. I wanted to spend the rest of my life with him, and a part of me still really does, but there is a huge part of me that doesn't."
The TV star - who was recently romantically linked to 'Gossip Girl' actor Chase Crawford, something she denies - also claimed she isn't ready to start dating again, but when she does she wants a man who is prepared to stand up for her.
"I need a man that's going to stand next to me and say, 'I don't care what anyone else says, that's my girlfriend. Shut up.' And not many people will do that."