What I thought was weird

I thought it was weird how Jake turned into a bad guy. And why did she say that she doesn't want him when they seemed to be in love not long ago? There was no indication the Ellie and Jake's relationship was in trouble except for Ellie finding out Jake had a few girlfriends from his past (its not that big a deal really).

Jake said he 'learned how to control it', so instead of using that plot for a happy ending, where Jake and Ellie and her brother all together learn to live with the curse, Jake teaching them all to control the transformation like he said he would.

They instead made up the part about killing the original will break the curse, when from all werewolf myths and movies there shouldn't be any cure (except suicide of course :D).

It seems like to me like the director/writer wanted to put another plot twist in just for sake of it.
And if Joanie was the werewolf why didn't they put any hints in. Nobody seemed to show any attraction towards Joanie even though Ellie was getting all this attention.

It just doesn't make much sense.