Future step daughter (am I wrong?)

Okay, so me and my SO have been together for almost 2 years. His daughter is 10 years old and I love her dearly. I just cannot stand to sleep in the same bed as her. It drives me crazy. I don't know why but it makes me uncomfortable with her in the bed with me. Am I wrong for not wanting to sleep in the same bed as her? I seriously love this kid like my own, but at the same time she isn't my child and I don't have any so it makes me feel weird. Has anybody been in the same position before? Thank you