Daughter does NOT want a sibling


6 weeks pregnant and she heard something that made her think that I might be pregnant. Rewind to last November after telling her that we were pregnant she flipped out. That ended in miscarriage, so this time we have decided to wait longer to tell her. When she heard what she thought was something about me being pregnant, she starting saying, I don’t want a sibling, and getting really anxious like she did last time. She’s 10 by the way. This breaks my heart. We have told her from time to time that we are trying to have another child, so it’s not like it’s all of a sudden dumped on her. I just don’t know the right things to say to her to not ruin her when explaining to her why we want another child. I don’t want her to ever think she’s not enough. Husband is not her biological dad, but bio dad only texts once a year. Suggestions?