twin kittens

Question
I have a set of twin boy and girl kittens. They are almost 8 months old.  My girl is the smaller and weaker one. She just started jumping on everything, tearing up bags and just acting abnormal for about 2 weeks now. They both explore and get into things but she is acting extremely wild. She's not biting or scratching people but when I'm not around it's like a zoo. I have 2 play centers for them to jump and climb I have two tall scratching posts and 2 on the floor.  They have balls to play with, ones that dangle, a swat toy, a partially encased ball and swat toy, a electric mouse and a sling shot bird that chirps. They both eat the same food but have different treats. I love both my cat and try to keep them happy but I feel like I am rewarding her bad behavior. I'm scared to give her away because somebody told me that she could die from grief but at this rate she's going to kill me. Please help!

Answer
Latifah,

Has she been spayed and the boy been neutered?  If not, this may be the root of the problem.  If they are not fixed, the sooner, the better!

I am not sure why jumping on things and tearing up bags is a problem as this is normal cat behavior in many cases.  Please explain.

Best regards... Norm.