How do i deal with it

I got together with my husband that had 3 kids that he had full time. I knew it was going to be hard because he had a 9 year old daughter which is 10 now. His daughter and i was so close for a while. Then Marques and I got married in the summer. Which his daughter was so happy about it. After the wedding the kids went their mother house. When they came back from their moms, things changed big time. She walked around the house with her head down. When i would walk out of the room she would laugh and carry on with her dad. When i walked back into the room she would walk off to her room. I tried scrap booking with her. Taking her to the movies and cooking with her. She seems to have fun until her dad walks in. I told my husband what has going on and he told me he doesn't see it, And that i should try harder. I don't know if she heard us talking or what but things got weird again. It go's on and on. I don't know what to do. How do i deal with it?

[Londres70]

How's the relationship with the ex?  The ex is aware you both are married.....correct?

"I don't know if she heard us talking or what but things got weird again."......Can you further explain this?