Jess was never really good with pain tolerance. Although she did get better as the game went on over the years, it was always one of her inherent weaknesses. Not to say that she was special because of that since there were others like Arianne that also had that.
Naturally, since this was still early on, Jess shouldn't have that much tolerance for pain.
Especially considering she was hit in the liver, which was enough down a normal person. The fact she was even able to keep her balance enough to retreat was actually very impressive.
Yet, she went a step further and pushed herself off of the ground.
Although this was a very good opportunity for Richard to seal the deal if he hit her while she was on the ground. However, he simply waited with his halberd on top of his shoulder. He was the kind of person that was hung up on honor.