Alpacky has a slower attack rate than Camelle, but she's guaranteed to survive a lethal strike, and when her health reaches 1%, her damage increases by 900%. In other words, when Alpacky survives a lethal strike, her damage multiplies by 10. Make sure that you either save a damage-dealing Cat Cannon for her lethal strike, use units with longer range than her, or with good timing, fast units will attack her before she can attack them.
Despite her strengthen, the overall strategy for Alpacky is no different from what you would use against Camelle: use tanky melee units like Jamiera Cat and Crazed M. Titan Cat to get real close and deal damage to her. Save your Cat Cannon for when she survives the lethal strike, and use it to finish her off. However, if you are unlucky, the ability will activate before the lethal strike. If that happens, use units with good speed like Crazed Giraffe Cat.