Even if you take a less generous view of the reasons and just assume the FA had become a little irritated with the teenager who appeared to be rudely ignoring her whenever she spoke to him. you still don't end up with anything worthy of a complaint.

It is helpful to let AA and cabin crew know about any special needs/circumstances so they can not only provide appropriate service and support during normal flight, but also so they can be aware and prepared in the event of an emergency.

So next time, consider that and perhaps make it a less stressful experience for everyone by letting them know enough to avoid any repeat of these issues...