^You also have to keep in mind that men and women have a different center of gravity.
Though, I really wasn't sure where you were going with that, haha.
Since I don't jump, I cannot say what works jumping a fence. However, I did ride with a forward seat until switching to a western saddle in late November. For me to feel secure and balanced when my horse got funky, I needed to keep my knees slightly loose and feel the contact in my calves, not my knees.
This was written in the 30s by Harry Chamberlin, who "was assigned to Fort Riley's Horsemanship Department and went on to compete at the 1920 Olympic Games with his mount Nigra. He was then sent to Europe to train for two years, the first year at the French Cavalry School in Saumur, and the second at the Italian Cavalry School in Tor di Quinto. While in Italy, he was introduced to the forward seat, which he brought back to the United States..." (Wiki)
Since it was written roughly 80 years ago, styles and thoughts on jumping may have changed. But for me, riding a somewhat nervous mare but not jumping intentionally, I found keeping my center of gravity above my heels a pretty secure position. My biggest problem was a tendency to grip with my knees, which created a pivot point. Then my feet would sling back, my body would go forward and I would be in a bad position if she spun or hopped.
Again, I do not jump
so the OP will have to decide if this advice is worthwhile or hogwash for her needs. I wish her well regardless!