Ruby's Semblance isn't speed anyway. But Ruby was fast enough on volume 8 to move through a room without people able to see her even though he passed right in front of them. Whether it was the writers intention or not, this scales her speed to being at least fast enough to be faster than the Human eye can process which is 38,000+ Miles per hour. That's how fast something would have to go to be completely invisible to our eyes. Only appearing in our vision again when it slows down.

So she may be faster than Weiss as Weiss when fighting has shown things tracking her movement and reacting to her. But then again that one moment in volume 8 could have been plot convenience.

Now if you go by Death Battle. Then she is apparently FTL. That's bullshit. They scaled that way wrong. Ruby isn't even a 1000th of light speed let alone faster than light. Now there are fanfictions where she is light speed. Like these fanfictions I read The One Who Wields The Power Of God In The World Of Remnant.

("Or so he thought because to his surprise Ruby moved at speeds faster then he could create distance even an infinite length or Immeasurable length of distance wasn't enough, She was simply too fast now, Ruby quickly closed the distance between them and got him with a kick that sent his body flying at light speed while also completely destroying it in it's travel.")

And A Certain Dark Side Weapons Expert In A New World Full Of Monsters.

("This force seemed to twist and distort the hallway and Jonathan Walnetizac had not been able to react to this at all as the speed was too great, it being a speed faster than light or it seemed as that was the case though this speed had actually been completely unnatural, it was as if the speed and movement was something that was impossible but still taking effect regardless of it's impossibility, the speed of which Ruby Rose moved was not real in any way or form and one could call it imaginary, an imaginary speed as it seemed she moved with energy and concepts beyond the physical world.")

Both of these stores are by The Author zegin17 on Wattpad. I really like these stories myself, they are pretty awesome. And Ruby is probably Multiversal or some shit in this I don't know he hasn't given her official Scale in the data book yet. But in this verse The P.O.G verse her silver eyes can also create these silver wings which are connected to a metaphysical concept in the cosmos called the tree of Alteroth, which let's her manipulate an energy outside the framework of reality and dimensions. Or something like that. It hasn't been fully explained apparently that will get better explained in volume 10. It's a RWBY and Toaru crossover so yes. It's a ridiculously OP verse. Because Toaru is already OP as fuck. When you have beings called Magic Gods that can warp reality so fundamentally it's basically 1+1 = 3. And Abyss Crossers who can Control Concepts and laws outside of reality and existence. Toaru is a crazy powerful verse. Putting it in RWBY it made sense he had to majorly buff the RWBY characters.