You had no other choice.
Your friend was being incredibly selfish and unreasonable.
I'd be furious with her. She shouldn't have shown up with a sick DC, and should have removed her without being asked the second it was clear she was sick.
When my child was young he had a health issue that made very bad for him to catch colds etc. No matter how many times you tell people, some just carry on with no regard. I had one friend in particular who would routinely bring her DC over full of cold. I would tell her to leave. Now I just don't invite her, even though the health risk has passed for us. I still don't want her child's fucking cold!!
I know the line you are walking between wanting to give your DC a normal life and social opportunities, always balancing that against the risk to their health. It's a decision you think about all the time. But it's your choice, people don't get to choose the risks for you just because it suits them.
Some people will never get it. They're too selfish to put themselves in your shoes and understand.
Let her be mad. Honestly, this would make me want to end the friendship. If you want to you could send a text
'Hi DF. I hope DD is feeling better. I know tonight was difficult and perhaps surprising for you but this is the reality for us with DD's health. To be clear for next time, everyday childhood fevers, coughs and colds land my DC in hospital. We don't want to shut DD away but we do ask for people to be conscious of not coming around DD when they are sick. I hope you manage to enjoy your trip. Let's chat when we're feeling calmer about it.'
I really hope your DC doesn't catch it.
Don't give it another thought OP, you did the right thing by your DC.