If you had expressed your thoughts to the priest, that might have been rude but just being near/in sight of one when you do, he didn't hear you, wasn't listening to you but to his own lunch partner like your friend was paying attention to her food.

We are not responsible for what we think, cannot control what we think, only for what we do. A child wishing his mother dead because he's angry at her is not a bad child! You currently deal with your stress in nervous, negative chatter, I think it is great that you had that opportunity, were with a "safe" friend so it didn't affect anyone. It takes practice to deal with our anxieties in helpful ways, to "get over" our problems so they don't disturb us as much.