I don't understand why people don't like this pairing, honestly they're cute together.
I can think of two reasons:
1/ The usual yuri-hater, the kind who will look at every opportunity to stomp it down.
2/ How Ooi expresses her love. To me it shows how strong her love is. But I can understand how that didn't sit very well with some people, it was kinda hardcore after all. How a lot of fan arts depict this "hardcore-ness" doesn't help either.