What do you think Hino is up to

i think she is messing with our head like we all have come up with alot of possible ending of vk

Not sure, however an estimation;
I think she tries to postpone the LT, as apparently it sells, but the danger it lurks here is that it can turn to a boomerang as the fandom has lost a lot of its patience (generally speaking).

The most fans are irritated by Yuuki's weak character (in general). While Hino handles good the male character (especially Kaname as a character that has mysteries, moves the plot) and so on, the main protagonist that she has is not convicing enough.

There are moments that I am thinking; "Is that deliberate? In order to grow her and show development?" like was this planned or is she delaying her plans in purpose? (because Hino has stated multiple times that she knows the end).

Can't tell. Hino speaks very little about her intentions. I wonder if all mangakas are so secretive lol (to tell you the truth I would not mind a small spoiler).

I think it'll be a sad ending so it would be something no one would forget