There is another post on this board where women with two uterus (and some with 2 cervixes) discuss their fertility
It is titled: pregnancy with two uterus
by sjis2much, Oct 20, 2006 12:00AM
Good Luck! I am sure you sister will be just fine.
I'm not positive but a friend of mine had this and her OBGYN performed an external exam first, then internal, then transvaginal ultrasound, x-rays and that was basically it. They removed some tissue sample to make sure nothing was forming bad cells. They also told her she had a really high chance of concieving multiples.