The twins are at odds but I don't think it applies to their respective members.
We've been told that the divide between both sides is a serious issue for the whole family and even the Ari family gets involved sometimes, so it's not just the twins beefing.
In any case, it doesn't change the fact that Yuri would have been more likely to meet Jinsung, who is supposed to be a traitor to the family, if he was closely related to her.
That's not a technique, it's just her throwing a punch really hard and giving it a name. It's like calling Parakewl's Revolution a technique.
Among all the Zahard Princesses from the Great Families she has the best gifts for physical abilities. I can't imagine her strongest move being a ranged one.
Or maybe it's precisely because her physical strength is so high that she never bothered learning complicated close range shinsu techniques when normal martial arts gets the job done for her.
We've seen her in enough pinches by now that if she could do that stuff she surely would have, but she never has.
It's not like she is a Wave Controller or anything. We know she is a Fisherman and Scout.
And? By the time you reach Yuri's level, pretty much everyone can use shinsu techniques. Karaka's a Scout and he's the same.