OK, yes, cysts can grow quickly. Yes, cysts can rupture, spilling their contents into your abdomen, thus causing pain and possibly an infection. In my case, my rapidly growing endometrioma (a type of blood and solid mixed cyst) damaged the ovary by crushing it out of shape.
My suggestion is to get that second opinion from a gyn and get more complete information on your condition. Why does your family doctor believe that a cyst, even a complex one, justifies a complete hysterectomy? The gyn can help you with that decision.
If it is definitely a cyst, there is much less to worry about. However, if it has both liquid and solid components it becomes more worrisome. I'd go to the gyno. to have it checked out. Seven months seems like along time to wait on it.