From my own personal experience I have lost my sex drive when I was no longer into the person. Not saying that is your case, just my own experience. Also birth control pills seemed to decrease my drive after a while. Since she is going to the dr it looks like she is ontop of the problem and wants answers. It could be an infection, depression etc... anything is possible. Good luck, I know I put my husband through hell for a period of time with no desire.