You keep replaying the moment you found out. Not because you enjoy it, but because some part of you is still searching the tape for a warning sign you missed, as if spotting it now would make you safer next time. It will not. What you are actually asking, underneath "how do I trust them again," is whether it is even reasonable to try.
Most advice here collapses into a script: communicate, forgive, move forward, or leave. Three thinkers on the Consilium roster would approach this from fundamentally different directions, and none of them would hand you a script.
Satir: start with yourself, not them
Virginia Satir would redirect the question before answering it. Not "can I trust them again," but "what happened to your own sense of worth while this was happening to you." In her family therapy work, she saw people respond to hurt by collapsing into one of a few familiar postures, placating to keep the peace, blaming to regain a sense of control, going numb to avoid feeling any of it. None of those postures rebuild trust. They just manage the immediate danger. She would say the actual work starts with restoring your own footing, so that whatever you decide about the other person, you are choosing it rather than reacting from it.
Feelings of worth can flourish only in an atmosphere where individual differences are appreciated, mistakes are tolerated, communication is open, and rules are flexible.
She would ask what atmosphere you are actually standing in right now. If your own sense of worth is still on the floor, no amount of reassurance from the other person will register as real. It will just bounce off.
Spinoza: understand the cause before you decide anything
Baruch Spinoza would say the hurt keeps resurfacing because it is still a passion, an idea you have not yet made clear to yourself. For Spinoza, an emotion stops controlling you the moment you form an adequate, causal understanding of it. Trust does not return through good intentions or the passage of time. It returns when you can give a precise account of what produced the betrayal, what conditions and pressures and habits made it possible, rather than a vague story about their character or your bad luck.
An emotion, which is a passion, ceases to be a passion as soon as we form a clear and distinct idea of it.
He would push you past "they're just like that" or "I should have known," both of which are ways of avoiding the actual mechanism. Until you understand the specific cause, the wound stays a passion, and a passion can be triggered by almost anything.
hooks: trust is a practice, not a decision
bell hooks would resist the idea that trust returns in a single realization, whether that realization is about yourself or about them. In her framework, love is not a feeling that either exists or doesn't. It is a set of actions, repeated. Trust works the same way. It does not come back because someone says the right thing once. It comes back, if it comes back, through a long sequence of demonstrated behavior: accountability shown rather than promised, honesty offered without being extracted, care that holds up under ordinary boring days, not just the dramatic ones.
To truly love we must learn to mix various ingredients, care, affection, recognition, respect, commitment, and trust, as well as honest and open communication.
She would ask what has actually changed in the pattern of behavior, not the language around it. Words are cheap the moment after a betrayal. Only repetition tells you anything.
Where they disagree
Satir would say the work happens inside you first. Rebuild your own sense of worth, and the decision about them becomes clearer because it stops being driven by fear.
Spinoza would say the work happens inside the event itself. Understand its cause with precision, or the hurt stays a passion that can be triggered again regardless of what anyone does next.
hooks would say none of that matters until it shows up as sustained, repeated behavior between two people. Insight without demonstrated action is just a better story you tell yourself.
Satir starts with the self. Spinoza starts with the cause. hooks starts with the pattern of action over time. None of them would tell you what to do.
The question you came here to avoid
You searched "how do you trust someone again after they've hurt you" hoping for a method, something with steps. What you got instead are three people pointing at three different places to look, your own footing, the mechanism of the betrayal, the pattern of behavior since. That is not evasion. It is the actual shape of the problem.
So the harder question underneath the one you asked: are you trying to figure out whether they have changed, or are you trying to figure out whether you are capable of being hurt like that again and surviving it either way?