The big pet stores, Petco, Pet Smart, have different brands. I used plain old whatever catnip and my cats used it. I bought one called Cleo's something or other, sorry, and they went APE!!! See if she can find one of the 'designer' brands. Midge may have very decerning tastes and expectations, lol. It's not that bad a price either. It was under $5 if I remember correctly and it lasts forever.My daughter says she doesn't seem to care much about catnip, although she has only tried dried, not fresh.
If she doesn't like it, our other cats will but she definitely has some weird problems. The other night she was just exploring at our house, and got up in my daughter's lap. All of a sudden she winced and yowled like she was in pain, but didn't look at her side, or whatever hurt, like you would expect. It was very strange.