Dreaming that someone is untrustworthy or a traitor can mean you're
feeling suspicious of them somehow in real life, or you're exploring a worst-case
scenario, or you're feeling paranoid or suspicious in general.
Your loved one betraying you can mean:
You're feeling insecure about your ability to hold their interest, or you're afraid of the idea of them cheating on you
You're feeling jealous about your loved one devoting time or attention to something other than you (work, a hobby, watching TV, using the computer, etc.)—having nothing to do with any actual cheating
Someone other than a romantic partner betraying you can mean:
There's someone in your life whom you don't really trust
You do not trust God (or feel God has betrayed you)
You do not trust yourself (or feel you have betrayed yourself)
