How do you give it to her? Does she actually eat it or just rub on it?
When we'd get catnip mice from the store, our old kitty used to just rub his face on them, but he never chewed them or ate the catnip.
She does both. The commercial kind comes all chopped up in flakes. If I put a little pile of it in a dish...well, more likely a plastic snap-on lid..she'll chomp on it for a while. If I put it on the carpet, she'll roll in it. I've got a Ziploc bag of commercial catnip that she likes to lie on.
This is Tam on catnip. Frightening, isn't it?