So how does a disabled individual go about making decisions on her sexual lifestyle? And does that mean she will never be able to decide whether she has sex or not. Not arguing just curious.
I worked for many years with the developmentally disabled; some who were extremely low functioning and some who were only mildly impacted. For those who were capable of forming friendships, they would often seek to have 'boyfriends' and 'girlfriends'. For many of the lower functioning individuals, this involved no more than holding hands, maybe kissing and being together a great deal. For others, it also involved sexual activity. Parents and guardians would talk to their children (who were chronologically adults) about birth control. Most of the women would consent to go on the pill; currently many use the shot.
These discussions are complicated and sensitive. These delayed adults are sometimes functioning at a very young emotional/cognitive level, so explaining the complexities of pregnancy, sexual responsibility is difficult. It is sometime not so much about making decisions about their sexual lives as it is the guardian minimizing the damage that can be done sexually to their child.
And as someone mentioned earlier, it is much better if this girl forms a relationship with someone who is developmentally on par with her. Certainly it has less legal risk.