The debate of who would win in a fight between a female lion and a female jaguar has no definitive answer, since the outcome of any animal-versus-animal confrontation would depend on factors such as age, size, health, gender, and temperament.
In general, however, due to their superior size and weight, lions tend to be viewed as more powerful predators than jaguars, and therefore may have the slight edge in a confrontation. Additionally, while jaguars can climb trees and are very agile, lions are incredibly strong and have the power to tackle their prey to the ground and hold them in place until they are subdued.
On the other hand, jaguars have several advantages over lions which could potentially win them an encounter—namely, their sharper teeth, stronger bite force, and increased agility and speed. Jaguars are also known for their ability to swim, which would be a useful skill in a fight, as well as their greater stealth and hunting capabilities.
In the end, it would likely depend on a number of individual factors, such as strength and agility, as well as the ability to use tactics and out-think the opponent, that would determine the outcome of such a fight.