I think 'I'm not a Plastic Bag' was definitely an It bag. In her book, an It bag is probably a bad thing, ephemeral and overpriced.
The "I am not a Plastic Bag" was probably a hit only in the UK. I never saw one in real life and could not care less, let alone queueing to get one. You can buy sturdy, supermarket canvas bags from any supermarket, therefore cashing out whatever this Hindmarch woman was charging for her bag sounds pretty silly to me.
Moreover, she is totally unknown in many European countries - for sure nobody ever heard of her in Italy, if you'd mention her name you get an blank stare. I really don't see her as an outstanding name in the bag business, regardless of her turnover.
Finally the only reason I know about her is exactly because Jolie was carrying an Hindmarch "It" bag - the same thing she is declaring dead is what put her on map in the first place. Quite hypocrite.