Try it. When a child acts out with animals, you have to be concerned that she might hurt them, and if she does, you'll have to wonder if they are a substitute for other things in her life that she would like to be able to affect and cannot. I'd talk to a children's therapist.
Annie Brooke is right. Your daughter could be angry inside and not know how to express it and at 5 certainly won't know how to deal with it, and this may be why she is acting out by being too rough with the kittens. I think counseling is an excellent idea.
I have given this a lot more thought and I don't think I will do counselling just yet. I like the idea of having just one at a time in the room with her. I don't know if she is being shown how to do it or just told, it was my understanding that she is just being told though. I will discuss this more with him. I do hope he downsizes the number of these kittens though because I just think it's too much for a 1 bedroom WITH a hyper child and at this point in our relationship we can't afford the conflict this is causing already.
Thank you guys for your input!