I would suggest blocking her. If she has come back after several months just to say you are sick, she has issues that you don't want to be dealing with.
Don't forget that you need practice changing diapers too. As said above get some cheap store diapers and get good at changing diapers before the baby comes. Above all else make it fun for her.
There is nothing wrong. ABDL is a broad spectrum. You do you and enjoy. Talk to your partner about what things that you enjoy and what parts you have no interest in.
Bad idea, talk to her first like aby suggested. Don't surprise her with a diaper. Also check out the Dream a Little podcast for information on sharing this.
I have thought about that before. Have a mommy that spoke another language just like she would with a baby. I would learn the same as a baby just slower.