Let's play devil's advocate for a moment.
Let's just say that if Zhen Zhen did not die in MDWAV2, would Tin Yau eventually have marry her? I mean if Zhen Zhen did not make Tin Yau really think whether he loves her or confused her with Ah Sau, like she did at point of death, Tin Yau may never know and thus may eventually marry Zhen Zhen.
Siu Ling and Tin Yau would not have happened then because Tin Yau is too faithful to deviate and Siu Ling cared too much for Zhen Zhen to hurt her.
Siu Ling may wait for another few years for Yau Chee Kit to return. Yau Chee Kit promised to try out for Siu Ling again in 5 years. Perhaps, she would have accepted him then.
It's just a thought of what may be...