Husbands daughter

Me and my Husband separated a couple days ago. He cheated and I left him and I am moving states on Monday. Well my step Daughter has been texting me. She is with her mom during the week and with us on the weekend. But she usually texts me. Well today she texted me and I’m just being normal asking her how is school etc etc. I haven’t told her anything that had happened and neither has her dad. Should I be texting her. Me and her have a very good relationship.she is 11 and been in her life since she was 7. Idk I still want a relationship with my step Daughter. This is not fair. I’m so mad at her dad.