Telling the step daughter

How has everyone else told their stepchild they are pregnant. I have a 10-year-old step daughter I’m am really close with and she has voiced her concern about not being loved anymore. She is the only child on both of her parent’s side. She also cries when we talk about children. We are unsure how to tell her. Any suggestions would be appreciated! ☺️ we keep telling her we love her and I see her as my own kid. But that goes so far... especially when her mother keeps reminding her I will never be anyone to her.