was it rude of me to say something rude about my best friend out loud when I was by myself?

so I have a best friend and she kind of did something today that made me a little upset and I said something like "she's always thinking about herself" (this isn't true I was just being dramatic) out loud to myself when no one was around. I would never say something like this about her around anyone because she's my best friend and that would be so rude of me, I would never talk bad about my bsf to anyone else but i just feel bad even though I didn't say it around anyone else and I know I wouldn't.