A Simple Question

I live at home with my wife and step daughter. Recently when my wife was at work and my step daughter at school I was sat on the bed in my room looking at my tablet computer with some porn on it and masturbating. I was naked from the waist up with my cock in my hand when I heard my step daughter come in from school. The door to my bedroom was closed so I continued on as I was pretty close. She never comes into my room and if so she would always knock. However today for some reason she came straight in opening the door wide. I was side on to her with the ipad in one hand and my cock in the other. I heard her gasp and say sorry then go to close the door again but she kept facing into the room leaving a gap of a few inches to talk to me through. She has never seen me undressed before never mind wanking so I was really worried about what she had seen. I apologized straight away and put my arm in front of my throbbing cock but the head was still sticking out above my arm and I could feel the heat from it on my bare skin. She said she was sorry she wasn't sure if I was in and was looking for me, she made some comments about school and all the while she was standing up on tiptoe, trying to get a better view I assume. Anyway she left and went to her room. I quickly got dressed and knocked on her door to see if she was ok. I said I was sorry she had seen me undressed and I hope it didn't embarrass her. She said "oh that, no that's fine I have no problem with it" so I left it at that. So the question is did she see it? Personally I can't see how she didn't and if so did she really not mind or perhaps even like it if she was trying to get a better view. I can't decide whether to raise it with her to find out what she did see and if she did see me masturbating was she really ok with it. Any thoughts anyone? I know this isn't a particularly exciting story but the thought of her seeing me wanking is really occupying my thoughts a lot at the moment.