I also had the same pain, stretching of the ligaments, was extremely uncomfortable especially at te end. Not too long left, good luck.
I had the same problem when I was pregnant with my second child around 33 weeks. My doctor told me from the stretching it was my ligaments being stressed and that when I sit I need to have my legs elevated so as not to have all the pull downwards and try staying off my feet.
Hmm it sounds like it a pain that is caused by ligament pain or it is just where she is sitting in there could be on a nerve. There is nothing you can really do about it--technically it is just a growing pain. Try sitting in a warm tub and see how you feel. The heat might make you feel better =)