My period definitely messes with my emotions, I get more sensitive, angry, sad, everything at once.
I believe that we should never make any decisions or take action when we are emotional, because we often aren’t thinking clearly and we tend to deal with the situation in a different way than we would normally have.
I know it isn’t so easy, and I am certainly working on that myself. I definitely fight more with my partner when I have my period and later see that I could have handled the situation way better.
It doesn’t mean that you should neglect your feelings, but wait until you are calm and in control of your feelings to talk to your friend.