I Believe A Guy And A Girl Can Be Just Friends

There is a special friend of mine and I met her in college 3 years ago. I see her as a sister: the sister I never had. We get along great even though I rarely see her now. Recently she started working in a restaurant and I've been eating there just so I can talk to her. I bring her cold bottles of powderade and water because its 110 degrees outside here. Our relationship isn't inappropriate and we've never even kissed or flirted. Problem is she has a boyfriend whom she lives with and they have a young daughter. I feel he has a sort of resentment or suspicion of me. In the back of my mind I feel as though this could threaten my friendship with her one day. I am not sure what to do...