Unless you dreamt about something crazy, people aren’t generally that interested in listening to you talk about your crazy dreams, let alone telling your ex. Out of everyone who could possibly tell me about a dream they had about me, I would least like to hear it from my ex. By them messaging you something like “I had a dream and you were in it”, they are just begging you to ask them to elaborate.
I bet they weren’t expecting their ex to pull a fast one on them like this, huh? I think that this person’s ex is only interested in finding out more about this dream if it happens to involve a knife, otherwise, she probably isn’t that interested in hearing anything about it. Hopefully, this does the trick to keep him from dreaming about her, or at least that with her.