Well, since I only read the Seiken no Blacksmith manga like 2 months ago (at least up to the recent translated chapters) I can list a few feats for Cecily.
First, she's about peak human in terms of speed and agility. She also has relatively good damage soak and while her strength isn't that much she took strong attacks with the assistance of Aria.
As for Aria, she can grant the following abilities to Cecily:
- Wind arrow: Cecily shoots a piercing arrow of wind which can go through buildings or a rather thick plate of steel.
- Wind blast: She can send a burst of wind which can destroy her opposition or counter opposing blasts. Small building to building elvel
- Wave of wind: Cecily thurst her sword down and releases a frontal wave which travels on the ground. Building level+
- Wind barrier: Cecily surrounds herself in a barrier of wind to tank the opposing attacks. Building level
- Wind burst: Cecily uses her sword to increase her speed for a short burst and assault her enemy with a strong frontal charge. Faster than eye level. (this move oddly resembles the thing which Saber
did in the 4th episode of Fate/Zero
- Wind enhancement: Cecily surrounds herself in an aura of wind which increases her speed considerably. Mildly superhuman level