Dana is aware that if she just stabs the kobold's, the same outcome as the first one, is what will end up happening.
But, if the Kobold has nowhere to get pushed back to once it's body makes contact with the sword, it will be forced in a standstill position while the sword has no choice but to get through its body.
She had pushed the kobold to the wall earlier so she could put her thoughts into demonstration, to see what results it will bear, and she was right.
It happened exactly as she had pictured it would. The kobold with its back rested against the wall, could not get pushed back any further, giving the sword the opportunity to go deeper than it normally would on its body.
Dexter was left speechless when he saw the outcome her thinking process led to.
He was amazed that in such a short span of time, facing a kobold for the very first time, she was able to collect information from it, and put it into practice within minutes of just gaining the intellect.