So I figure Cassie will get the same sort of treatment. If I had to hazard a guess, I would think she will get flight, heightened agility and speed, and low level strength and durability. So she'll do the whole "Bullets and Bracelets" thing, and be stronger/tougher than most, but not enough to step on Conner's toes, who remains the team brute.
Actually, has Diana been shown in combat at all? One would assume that Cassie will have a similar powerset so that could answer the question of Cassie's abilities.