It could be a lot of things so she needs to go to a doctor to make sure. It could be anything from a tipped uterus to cervical cancer, but she needs to go to a professional for sure and if I were you I'd be making the appointment ASAP :)
I think you need to see a counselor, and I mean this in the nicest way possible. There might be something going on that you have no idea about, that could be causing you to feel so upset when this happens. I would suggest going as soon as possible because your behavior could drive your loved one...