I have seen it a few times. Could be she was abused a in past relationship or even as a child. Or has been burned really really bad a few times, and its probably her wall put up, if she has sex that wall comes down and she just might be scared to death. I went almost 7 months with a woman with this a few years ago, and was patient, she had some serious issues. Some issues are so bad though the sex when it does come may never be good, because she may be very reserved in bed.
JUstin_Jackson