I will proceed to do a bunch of calculation stacking starting right now. Blind yourself if you happen to be serious about fictional calcs. I consider all of this canon.
Valentina's Perception Speed
"Valentina can calculate 10^54 different possible outcomes of a scenario in under a nanosecond."
10^54/10^-9 = 10^63 total calculations per second.
1/10^63 = 10^-63 seconds per calculation.
Moving 1 meter in the time it would make her to do one "calculation" would be:
1/10^-63 = 10^63 meters per second. 3.33e+54c
Appearing Invisible to Valentina
Since Valentina's perception is already 3.33e+54c you would need to be much faster than that to appear completely invisible to her.
I will assume you would only need to be around 4.45x faster than that for her to be completely unable to keep up. Base on the difference between human speed and human perception.
Therefore, anyone who outspeeds her perception will be assumed to be 1.48e+55c
Umami's Cutting Speed
Umami was stated to have cut between every atom on Phoenix's body before Valentina could react to her.
There are around 7e+27 atoms in the human body, meaning Umami would have swung her sword the same amount of times.
Assuming the distance her swung her sword was around 1 meter, this would be moving 7e+27 meters in 10^-63 seconds.
7e+27/10^-63 = 7e+90 m/s or 2.3e+82c
Valentina's Upgraded Reaction Speed
Valentina states for herself that her new body can calculate a well over googols worth of calculations per second. 10^100
Ian is fast enough to cross the Ark world 307 times before sealed Umami could react to his movements.
Sealed Umami can see her attacks perfectly clearly. And she attacks at a speed of 7e+90 m/s
Her perception is likely around 4.45x this: 3.1e+91
Moving a meter in this time would be 1/3.1e+91
= 3.1e-91 seconds
The Ark world is 25000 kilometers in radius, making its circumference 157000 kilometers.
157000 * 307 = 48199000 kilometers traveled.
= 48199000000 meters traveled.
48199000000/3.1e-91 = 1.5e+101 m/s or 5.1e+92c
Upgraded Valentina scales to 4.45x this as she was able to blitz Ian [2.3e+93]
Vima crosses a pocket dimension
Vima's pocket dimension is 473050000000000000000 meters across and she casually crosses it before Valentina can react.
Valentina's perception is 10^100 m/s.
473050000000000000000/10^-100 = 4.7e+120 meters per second or 1.56e+112c
Valentina later adapts and surpasses this speed.
Vima crosses an even bigger dimension
Vima creates and crosses a dimension spanding a googol meters before Valentina can react once again.
Valentina's reaction speed: 4.7e+120 meters per second.
10^100/4.7e-120 = 2.1e+219 meters per second or 7e+210c