The versions people describe
The same image arrives in a few different shapes, and the shape is where the meaning lives. Find the one closest to the night you had.
1Why did it feel so real, and why am I still angry?
Because the emotional part of the brain does not label dreams as fiction while they run. You genuinely felt betrayal, and the body stores that feeling the way it stores a real one. The residue can last most of a day. That lingering anger is a physiological hangover, not a verdict, and it fades if you do not feed it.
2What is the dream actually about?
Usually about closeness, not fidelity. These dreams cluster around periods of distance — long work hours, a phone that gets more attention than you do, a fight nobody finished, a stretch without touch. They also cluster around your own insecurity after a life change. The theme is fear of losing your place with someone, which is a different problem than betrayal.
3Should I tell my partner about it?
You can, if you frame it honestly. Say what you felt, not what they did. Something like this works — I had a horrible dream and woke up missing you, can we have an evening with no phones. That opens a door. Leading with the dream as a charge closes it, and usually ends in a fight about something that never happened.