Temperature and Body Issue?

I’ve heard about this issue, and I am curious to know why it happens. A girl has been having an issue where overnight, she feels it is cold, but then next minute, she feels it is hot. So all night she’s tossing and turning until she wakes up only to find that her nipples are hard and that they hurt. Might this be constant temperature change? Might it be the tossing and turning so much? Maybe the fabric of the bed or clothing is irritating her nipples? What do you think?