To be no spring chicken is to be well past youth, and in this context the woman is indeed quite old.
Context: "And while the woman was well past her youth and a bit too tall to make most men comfortable, she was still worth looking at."
Hypothesis: And while the woman was no spring chicken and a bit too tall to make most men comfortable, she was still worth looking at.
Based on the context, is the hypothesis true, false, or unknown?