Vina:
This is based on my own observation; the drama shows she has conflicting feelings for TSJ and XL. Her promise not to love someone for 15 years is just empty words right now. Even TSJ in the drama knows that she is not completely in love with him; that's why he wouldn't kiss her. To him, it's just pity. I hope they made it clear that she really feels a strong love for him because, at this point, he loves her more than she likes him.
Dude.. didn't you watch episode 19? It clearly shows she's not in love with XL. She said she's scared of him, if she loved him she wouldn't be afraid of him.
The 15 years promised isn't empty words, when XL pulled her underwater so she would placed her lips on his for air, but no she rather die then do that. She even told Jing in the cage. "To keep my promise to you I swam in the sea all night. I felt like I was about to drown and when I was almost suffocating I suddenly regretted it. I was wondering if a promise is more important than life. But the moment I saw you I didn't regret it at all." See she kept her promised with no regrets. They would be empty words if she did kiss XL or other men, but she rather die then touch his lips
Did you not she how angry he was after she said if she accidentally let him in her dream it would be more terrifying than death. He freaken tortured her making her swim the deep sea, she was so exhausted she went under and almost drown. When Jing rescued her and carried her to shore XL was watching. He then clutch his chest in pain because he and XY aren't together and the bug was hurting him.
Jing not kissing XY isn't because he thought she was completely in love with someone else but that he's afraid she was pitying him. Thats all. It just mean She hasn't proven herself to him yet.