Steven is desperate
From my perspective (you can correct me if I'm wrong) calah was inlove with Steven, but it was a slight turn off for him because he liked to chase rather than when it's mutual. Allie on the other hand didn't like Steven but she was going with the flow and saw what she can benefit from the relationship and you can tell she's disgusted by Steven from her facial expressions, and that's exciting to Steven but the reason why they broke up, is because Steven went public with the stagecoach debacle, if they handled it privately they would still be together even now. To me Allie looked at the bigger picture, saw what she can benefit ( there's nothing wrong with that) and I'm sure he has been a weirdo to her even before this and she tolerated it, she was going with the flow to me and that's 100% okay. Afterall Steven is a weirdo and no women should be with such a man.