hey Willo, I think it is fair to say that most of us were in the dark about cervical and other gyn cancers before we experienced it personally
So, please, do not worry about that. The only reason I brought it up in the first place is that I had never seen anything regarding the depo shot discouraging cervical cell changes. I think it is very telling that you are concerned about your sister - I think you have the feeling in the back of your mind that something is not right? I know what you mean, the thought of leaving cells on the cervix that could possibly progress to cancer, is very frightening. I am guessing she had low grade cell changes or maybe atypical cell changes. In that scenario, it is very common to repap in 4 to 6 months to keep an eye on them and see if they regress. It is very common for these types of cells to regress.
The pap can pick up cervical cell changes, but it also can sometimes pick up endometrial (in the uterus) cell changes as well. When that happens, they get a bit concerned, especially if your sister is younger. The d&c would be quite appropriate then, to examine the lining of the uterus to see what is going on. My mom, in fact, had this happen last year, and had to go for an endometrial biopsy (versus a d&c) to make sure nothing sinister was happening with the lining.
I can speculate all I want about your sister's situation, but I don't know all the facts, so I won't make any more guesses. I think it would be a really good thing for you to continue talking to her about the cell changes and see if you can find out any further information. There is quite a bit of information out there about cervical issues, dysplasia is the technical term for pre-cancerous cell changes, as well, you will see terminology such as CIN (cervical intraepithelial neoplasia) with corresponding numbers for mild (1) to severe (3).
Please, if you have any questions about cervical stuff, feel free to ask them. When I pop in again, I'd be more than happy to discuss them with you. I'm not a doctor, but I read alot about this ever since I got my diagnosis and have a good working knowledge about this stuff.
Take care, Willo.