Certainly I think that any of the group of which Rosalind and David are a part have to be strong, resourceful and self-reliant to live their life of deception in an atmosphere of such danger. However, you also might like to think about how she is presented as being a weak character. A key moment for this comes when the "spider-man" says he will take her as his lover:
It was not surrender to the stronger character, the conqueror. It was loathing, a horror which broke her defences from within.
This clearly shows that she was "terrified" and is made to be described as a "child" in the face of the thought of bearing this man's children.
However, you are right in many senses to point towards her strength and self-reliance. Note that when David, Petra and Rosalind flee it is Rosalind who has organised and packed everything and Rosalind also comes up with a "story" to explain how David and her were able to "hear" Petra from so far away. Although there are examples of her fragility, it is her strength that dominates.