how do we get this in game?

Well done!

yeah there is a number restriction (7 for idle) and the valkyrie in RO, like most monsters in this game, has 6 idle and/or walking animations. Knowing that flying monsters in RO have the same walking and idle animations.
I already had to duplicate one animation to have full idle animation number. and I did the same with the walking animation, that's why I can't really change that without her movement becoming strange and unnatural. Plus, LoK was not made to be speed up in the first place (they added this option only recently) and that is to be seen in every monster skill and movement animations.
The devs said they would bring more tools for modding later, hopefully I would be able to change this (if I have the time) when it comes out.
Thanks for your feedback anyways, it's always a pleasure.

I do not know how frame counting works in the keeper, is there any restriction on frames, if not, is it possible to simply duplicate some frames? This should slow down the idl animation

due to the difference between Ragnarok movement mechanics and LoK, I can't really change the number of frames, without it getting "unnatural" and "odd". Sadly I can't really do anything about it. I'll try to do something but I can't promise I will be able to. I'm not an expert and I don't really have much time anymore due to certain personnal circumstances.

Can you slow a bit her animations of flying? at x3 speed it is annoying eyes
Still looks cool it this style