The ending

It's open to interpretation, I suppose, but I don't actually feel this was an allegory. The kid straight up killed little animals in his youth. The main character assumes the woman must know, since they were all childhood friends, and he doesn't understand why she tells that story about her dream as if she doesn't know.

The dream itself isn't her being scared, then being comforted. It's her being scared, then being lured into a false sense of security before being killed. She was describing letting her guard down only to have the one she trusted turn on her. The main character was confused and bothered because she seemed to understand that marrying him meant he would eventually kill her, but ultimately, she was her own kind of twisted in that she loved him and happily wedded him regardless. That's reflective of the last shot, with her throat slit in her wedding dress as she smiles. I don't think that part was literal, but rather an indication of what's to come.

If you want to go the non-horror route, it could also be that she understands love doesn't last and can lead to betrayal. That she's giving him her life at the cost of her own freedom. But why the emphasis on the guy's underlying psychotic behavior if it's just a metaphor? Regardless, whatever ending is satisfying to you, that's the one you should stick with. ^^