Sinclair is easy to beat provided you don't let her pull off all those highly damaging saber specials.
The key-word here is close combat (melee), and Ryo is one of the best candidates for that.
From the very start of the round, close in to her and hit her with some of Ryo's simple chains, like f+A,A,B or f+A,A,C,C (my fave), etc. If you keep at it, she won't have a chance to do her saber swirl which is one of her most efficient attacks. Also, use the b+C Parry on her for her high saber hits which knocks down without damage but it comes in handy to quickly turn the game.
If you want to connect with a jumping attack/combo, don't jump at her diagonally, it's better to close in and then do vertical jumps + attack.
What's more, some/most of Ryo's chains and specials knock down (like the b+C), so always do a Pursuit Attack (df+A or B) afterwards to get an extra hit.
Another tactic includes taunting, which drains her spirit gauge so she can't do any damaging specials anymore, followed by forward dashes + close combat to keep initiative. Of course taunting has lots of drawbacks, but I thought I'd list it because it's typical old-style AoF cheese...
