Oh Baby, Oh baby O

My flatmate and I get along really well and rarely have issues with each other. We both are quite laid back, have high tolerance, plain speaking, and have few pressure points relating to our domestic geography. The one issue and discussion we had was last year, when she was inviting persons to our flat for dinner and such but not informing me. I would come back to the flat on school nights to find various friends over, and her using the kitchen and such, and I had no prior warning that there would be other people in flat. This pushed my button because I am a very private person and have an almost tangible sense of privacy (yet somehow i can blog quite openly? ponder the paradox, i am starting to...). I can feel people's energy and if I don't know them, and if they are in my domestic space, then that feels highly intrusive. It is as if my metaphoric hair starts standing on end. To solve, I requested that she send me a text if she was having guests over so that I could orient my expectations. I would expect myself to do the same for her, although she didn't reciprocate on this issue. However, she thought that the request was violating her freedom because it was "telling her what to do". Me asking her to text me if she was having guests, especially on a school night, she felt was being overbearing and telling her what to do. My argument was the flat is our space, and both of us have privacy rights, and if strangers were going to come over, fine with them being around of course, but please let me know in advance so that, basically, I could prepare. Or, perhaps call it, aligning my expectations. We had to go back and forth on this for awhile. But, we came to an understanding. Or at least she would then text me if she was having persons over.

Last night, I arrived at the flat a bit after 8 having gone to the gym. MF (my flatmate) had not been to our flat all weekend and I hadn't spoken to her for a few days. I opened the door slightly listening to determine if she was home. I was greeted by the loud, husky, repetitive sounds of her having an orgasm.
Nothing wrong with the Almighty O. I wish she and I were better acquainted. But its just not what I want to be hearing when I get home, low blood sugar and sweaty in a state of half gym dress half work dress. Turn head towards the bedroom area, and see that her door is actually cracked open 8 inches. Great, I can't then get to my room without passing a scene from an Amsterdam sex show. And of course the continuing screams indicating very good shagging; again yeah for her. But if she had texted me about her entertaining that evening, A she could have timed the shagging to be when I wasn't there and B I could have been better prepared to deal with the unexpected Too Much Information moment. But she didn't.

So, I turn left, go into the living room and kitchen area, quickly turn on some music, shut the door to the hallway and put my things down. My temper is flaring though because I feel I can't even go into my bedroom, where I want to go to dump stuff and change into comfy jammies. But I am, by virtue of wanting to avoid awkward situation, corralled into the western portion of flat. I start cooking dinner, finish dinner, eventually tippy toe to my room, put on more music, and go to bed. At no point do I see FM that night or this morning.
My Personal Life Agenda now has Meet with FM: to discuss last night on it. However, I am not sure really what to say. I need to avoid her button which is telling her what to do. I don't want to sound lecture-ey either. But I do want to bring up our agreement, and that last night made me feel really uncomfortable, kept me out of a portion of our flat, and that it could have been a much less awkward situation if she had let me know beforehand, or if she had asked when I was going to be back at flat. I am just not sure how to say it in a way that won't get an immediate angry reaction. How should I handle this? I need to step away from the hissy fit line, and into the humour playground. Please fill out your comment card….