A lot of people assume this is the correct way to speak because it's chronologically correct, but the general consensus in the trans community is that she was always Chelsea Manning, and always was a woman, and the time that she spent using the other name and gender need not be reflected upon. I do not know how Chelsea Manning personally feels about this, and every individual is entitled to their own respect, however the general etiquette when you do not know is to NOT deadname or misgender them, regardless of what era of their life you are referring to.
This is not an attack. Just a PSA.
Have a peaceful evening.
A squizard?