The blood travels at a maximum speed of 50km/h. She can only conjure one blood orb at a time and this orb follows her wherever she goes. The orb can’t go further away from her than a meter at maximum and it grows in size depending on how much blood Valentine is currently controlling. She can only control roughly 11 liters of blood that is stored in the orb. (The amount of blood in a person is equal to a maximum amount of 5.5 litres.)
She needs to focus to control the Marionettes, because of this she needs to move slower while she maintains control over the two. Marionettes can't dodge, parry or block attacks, they are only capable of simple movements, see: Zombies. They don't really have much power either, maybe as strong as a bare-fisted guy who doesn't know how to box.
The difference between moving her own body and controlling the Marionettes is that those are bodies which are not her own. Hypothetically speaking: If your consciousness was moved to another being's body which had extra body features like tails or wings you wouldn't be able to use them, or use them effectively. Controlling the Marionettes is somewhat similar. It's an foreign body that she has to control, so that is why she needs to concentrate on the Marionettes whereas controlling her own body comes naturally.
The maximum range she can control the Marionette is 20 meters maximum, point of origin is Valentine herself. Using blood to reanimate a corpse uses up the blood in the process, meaning she can't reanimate one corpse, let it 'die' so she can block an attack then quickly transfer the blood to another corpse.
She can only use fresh blood to reanimate corpses, so if she tried using blood that has been used to reanimate a corpse, there would be no oxygenated blood cells left to power the muscles to move.