This is actually a pretty tough battle. Bastille might be too strong for a 1v1 but if you think about it Revan beat her in a few seconds if you read the comics of Kotor. Revan was probably around Yoda's level possibly higher. However Rey and Kylo seem to have a battle connection with eachother and the battle would probably be like a Anakin and Obi-Wan vs Dooku. So head canon wise I think the duo would come out on top. I'd have to say Bastila from the feats I've heard of and seen in game would be around Dooku/Maul's level maybe slightly weaker.