How do I appraoch this from now on Christians?

[cmloem'mjamem]

My Christian friend of over 10 years and I talked today at work about a subject that I felt wasn't right or simply didn't want to answer to. She asked me was my boyfriend and I having sex. I simply answer the question, " I don't want to answer that." She immediately answered that she knows my boyfriend and I are having sex. Too make her understand that it wasn't her business in the first place to ask me that, I told her that I don't even tell my mom that my boyfriend and I have sex. I'm grown and over 18 years old and so is my boyfriend of 1 year and 6 months. I didn't get offended, but immediately shrugged it off after I had my boundaries up. She went on and on about the bible and what God says. I simply told her that what I do here, it'll be between God and I and not you at judgment day. I didn't get rude with her, but I wanted her out of my space that she was simply invading with her spirit of discernment as she felt with me. I also told her that I don't want to mix pleasure with business; Meaning, I don't want to go to work talking about my boyfriend and I if I didn't ask for advice or an opinion. I figure that if my boyfriend and I have a problem, we should be able to talk it out and handle it on our own; You know? I never said that I wouldn't need advice or support from a positive peer, but there are somethings better left unsaid because I have never asked this friend of over 10 years about her husbands personal sexual life. She also assumed that I didn't need advice from others about a certain problem if my boyfriend and I has one. I just felt this wasn't right and was very impolite. My thing is, there are somethings better left unsaid and this was one of them. I forgive her, but I don't want this issue to come up again. At times, I use to tell her about my boyfriend and I problems, but in time, I learned that somethings are better left unsaid. I have taught myself don't tell them what you want them to hear, but tell them what they need to hear. At times, I can say too much, but I'm aiming to do better to control what I say and how I say it, but back to this. This was way out of line, don't you think?