I agree with a lot of the above: tell her. However, I’m scared it won’t go that way. Hook went and told the gang about Neal in the cave in NL right away. Instead, when he went to Emma’s house, he told a bunch of lies.
This time around he’s afraid that telling her could get her and her family killed, so that’s probably the main thing holding him back. However, if he truly believes in her, he should still tell her and believe that she can fend for herself just fine.