This is how Hook knows it’s true love. This moment here when instead of Emma staring at Hook when he makes a romantic declaration, she acknowledges it and accepts that he loves her and that she wants to him to know that she feels something back.
If it were unrequited love, Emma wouldn’t say anything at all or even give him false hope. But she lingers long enough to let him know that she cares for him too and even Emma caring for him, is a start.