Should I be concerned about my boyfriend's 10 yr old daughter?

I've been with this gentleman for 2 1/2 years and recently my two kids and his three have consolidated households. I've spent a lot of time with his 10 year old daughter and feel she is WAY advanced in a lot of areas. I think he is a great father and she was always Daddy's girl that got away with everything until I came along. I get along great with her, but when she's with me and him she's always watching our hands and if we kiss in front of her she always looks at his genital area. She barges into the bedroom to use the restroom but she like side eyes to see what were doing. Then she made a comment to my 14 year old son about seeing my hand in her dads underwear while we were sleeping and that she wondered if her dad had a big ***()? My son was more was more disgusted with the fact that she was so interested. I feel grossed out and I need to know if I should tell my boyfriend??