It's not too late to address this. Say to her "I needed some time to calm down and compose my thoughts and now that I have done so, we need to talk. It is not okay for you to come in and inform me I need to change the tv from something I am watching to something your DD wants to watch. It is also not okay, when I decline, to sit at the table and loudly tell her how selfish I am. It is not selfish of me to want to use my tv to catch the last 30 minutes of a movie, especially when you have an extra tv in your room. I don't want that to happen again."
I get upset handling things like this in person so I'd probably have to write a note and end it with "I'd like to move on from here and don't intend to stay upset. I hope you won't, either. If you'd like to talk more I'm available."