I'm sure there are lots of lessons to be learned (such as don't promise a product in "early 2015" in September 2014 if you can't deliver), but I'm not sure why Angela Ahrendts is taking the brunt of the criticism. Most of the screw ups lie with supply chain management.
If you are Angela Ahrendts, you are dealing with overwhelming demand over the most diverse product lineup in Apple's history, and a shaky supply chain. Whatever you do, you will be criticized for it. If you cut off pre-orders and force everyone to join lines at the stores, you'll be criticized for not having pre-orders for a product that was announced 7 months ago. You'll also be criticized when the initial supply runs out in hours or even minutes, and when only the "wrong" combinations are available in order (e.g. you ordered a bunch of regular aluminum watches and everyone wanted the space gray). If you try online-only, as Apple essentially did, you'll upset those who woke up early and are getting their orders later because they ordered the models you didn't produce enough of beforehand. Apple actually tried to accommodate with the try-on appointments. People complained because the appointments started after the pre-orders mostly sold out. But if the appointments started a few days before, people would have complained that they couldn't order the product even though they just tried it on.