If she stabs him in the chest and nicks the aorta, the blood will spill out into the chest cavity but not much will leak out through the wound until the chest cavity fills with blood. The same would apply if she stabbed him in the abdomen.
If your woman uses an especially fine-bladed letter opener (I have one that looks like a miniature samurai sword--the blade can't be more than 1/16th inch thick at its thickest) even less blood would escape the wound.
Another thing she can do is leave the knife in the wound. It will act like a cork in a bottle until it's pulled out. Then the blood will gush.
I would imagine stabbing him in the eye would result in considerable blood spillage as the eye is heavily supplied with blood through a network of small vessels.
Hope this helps.
Dave