The first thing you really need to do is take all the glass off the tree! I learned that the hard way last year.
There are a couplr things you can do.
First, if possible, put the tree and the cat in seperate areas of the house and shut the door in between them. I know this is probably not possible so..
I have heard it suggested to tie the tree to a wall or some thing simalar. This way it can not fall over.
I also have heard it suggested to put tin foil under the tree and they wont walk n the tin foil. You can also buy a couple of those cheapy clear plastic mats or runner rug type things. They have little spikes on the back the keep them from slipping. Turn them upside down and put them under the tree with spikes face up. She may not walk on this either.
You can buy a mat that is supposed to keep them out from under the tree to, I really do not remember what it is called though.
GOOD LUCK! I had two one year old kittens last year, they were horrible!! Now I have a new 7 month old kitten plus 4 6 week old kittens. It is a nightmare! I almost want to take the tree down
The good news is my two older cats (they are now two years old) have not messed with the tree at all, so they do grow out of it.