This is a great question as it forces us to examine Rosalind's character more carefully in the novel and consider the role that she plays. Clearly, the fact that she is living as a deviant in a society that would punish that fact with sterilisation and exile means that she has had to develop traits such as strength and self-reliance very early in her life. These become evident in a number of different locations in the novel. One that comes to mind is how in Chapter 11 she takes the lead of the group of telepaths after Petra devastatingly summons them all to help her and protect her from a wild cat. Note how she takes control:
"But we must be careful this doesn't happen again. David will have to explain to Petra in words and try to teach her to use some self-control. If this distress of hers does occur, you must all of you ignore it, or, anyway, not answer it. Just leave it to David and me. If it is compulsive, like it was the first time, whoever reaches her first will have to try to make her unconscious somehow, and the moment the compulsion breaks you must turn back and cover up as best you can. We have to make sure we are not drawn together into a group again."
Note here how she shows her strength as a quick-thinking leader, even being willing to entertain extreme solutions to prevent the danger the group have just placed themselves in.
Likewise in the next chapter, Chapter 12, we see her strength reflected in the careful planning and preparations she has made for their escape, in sharp contrast to David's lack of preparations:
I realised that Rosalind had put in some careful planning to hide our tracks.
Thus, throughout the novel, Rosalind is presented as a strong female character, who shows self-reliance and leadership skills as she, like the other telepaths, is engaged in a desperate battle for survival.