Skillwise the opponents she's defeated, stalemated and held off are on par with Bulq handling himself well against Mace. Forcewise causing avalanches and collapsing large stalagmites should be on par with landing a force push on Mace ( imo ) and physically she's rather impressive with moving a large stone pillar off of herself and instantly crushing a droids head with a kick along with managing to push back Grievous with a physical stike, managing to weave her way through a hail of blasterfire, showing off insane durability and resistance to kinetic force in her numerous fights, being able to handle multiple highly skilled opponents for extended periods and generally keeping up with some of the best Jedi and Sith in the Clone Wars.
I think the fight depends on numerous circumstances. I'd have to consider if I believe Ventress at the time of her fight to be close to her prime. Also is Ashoka Tano in her prime here?
*Shrug* I don't know. There are too many factors to consider. I don't know how Sora's fighting style might effect the outcome of the fight. It'll be close either way.