You know because you love even when you’re hurt. Especially honoring and respecting their wants and needs even when they include “breaking up.”
You love if you don’t get defensive, insecure, or manipulative. If you don’t keep score. If you don’t hold grudges. If you don’t “take back your love” as punishment.
You don’t feel love. You DO it. It’s an act, not a feeling. It’s a moment by moment decision and re-commitment. You know because it’s deliberate and conscious.