Kate, this is one of many struggles ahead of you.
Enjoy your transition.
I highly suggest being even more forgiving during transition than you were before.
Why?
Because if your friends want to be around you, they are not as bigoted as some people can be, and early on it is good to have your friends, even if they may not entirely get or understand what you are going through. Transitioning all alone is a terrible struggle for most people. We tend to do better when we have access to friends, in spite of their faults.
Friends can be educated. Be polite. Have a sense of humor and be encouraging, at least for a while. This is NOT just to give them time, it is to buy yourself time. You need time to make new friends, and you can't do that alone. Your old friends will learn from your example but also from the examples of others.
Your one friend who used female pronouns in private? Perhaps talk to them and ask them to help you with the others. Explain that if you make a big fuss about it, it may make everyone defensive, but with their help, simply by calling you the proper things in everybody's presence, mountains could be moved.
Really though, gentle corrections work wonders. If someone calls me Tommy, I just say, "I am working with Tori now." I do not need to make a threat, or tell them how bad they make me feel, or shame them. The point gets made, gently, and they tend to conclude that they should call me Tori if they don't want to see my She-Hulk.
Pronouns are small beans compared to the other ways people can and do hurt trans folk, especially when we do not pass. If you don't learn to forgive even better than you forgave before transition, especially over the small stuff, you could be in for a world of hurt when the big stuff comes around. Things like overt bigotry and physical harassment make things like pronouns pale in comparison, and if you don't learn how to handle your friends' mistakes without upsetting them, how on Earth can you handle a potentially dangerous situation with a bigot?
I hope that makes sense. There are some lessons in transition you do not want to learn the hard way.
Aloha
Tori