Recognize what makes this moment difficult
Acknowledge the event directly without turning it into a lesson, comparison, prediction, or silver lining. For a message about how to support someone after relationship infidelity, use this factual base: acknowledge the loss as they describe it and notice the immediate housing, childcare, work, or social impact.
Offer support that can be accepted
Offer one specific form of practical or emotional support and make clear that no immediate reply is needed. Offer one practical task or a form of company that does not require them to retell the story. Make the immediate next step clear enough that the recipient can answer without reconstructing the entire history.
Follow their pace rather than yours
Do not attack the ex, push dating, demand details, or share the news before they are ready. For abuse, stalking, housing danger, child risk, self-harm, or immediate danger, connect them with specialist or emergency support. The recipient decides whether they want conversation, ordinary company, practical help, professional support, or quiet.