Wondering...

She is a truly wonderful girl, and an amazing mother.
My only problem with her is that I crave more love from her than she is willing to offer me.
I know that she behaves as if she was still engaged to that lying scum, and I wonder how far down the list of priorities I am. She loves him, that much is for sure. Last night I slept in her bed and held her while she slept.
I did not expect anything from her, yet, something odd occured. In the middle of the night, while I lay behind her holding her closely after gently tickling her back, she started rubbing her rear against my scrotum. I did not react at first, as I did not suspect the movement to be sexual in anyway, and I was part asleep myself. She then started moaning, and I, in my lulled condition was only half aware of what was happening. I, of course, reciprocrated, being unable to say no to her, and it immediately grew to full-blown sexual intercourse. After she had reached release, we switched position, she now being atop of me, as this was the only way for me to lose myself in the sensations enough to gain relief. Just as I was reaching my climax, she froze in mid-action and slid off. I, still slightly dazed, saw that she was sitting with an extremely disturbed expression on her face. We went out to smoke, and I tried to press the issue, but she did not answer. What made her stop, I wonder?