This study introduces the Beach Safety Hierarchy Assessment Scale (BSHAS), a 25-item self- and partner-report instrument measuring five theorized levels of nervous system readiness for relational engagement in individuals with dissociative identity disorder (DID), post-traumatic stress disorder (PTSD), and complex PTSD. The model proposes that relational safety operates hierarchically: Physiological Safety (L1) and Emotional Safety (L2) must be sufficiently established before Relational Safety (L3) can support proximity, and that Relational Safety does not imply Cognitive Engagement (L4) or Reflective Integration (L5). Data from 160 dyadic pairs (N = 320; 160 self-reports, 160 matched partner-reports) recruited from trauma-focused online communities supported the hierarchical pattern. The strongest finding was the L3-L4 gap: among respondents with relational safety online (L3 > 3.0), cognitive engagement dropped by an average of 1.31 points (p < .001), confirming the model's core claim that calm relational presence does not equal cognitive readiness. Levels 1 and 2 demonstrated discriminant validity (r = .28), supporting their distinction as separate constructs. Dyadic concordance was strong across all levels (within-pair r = .73-.85), with a consistent directional bias: partners perceived more physiological activation and less relational/cognitive access than individuals self-reported. These findings provide preliminary empirical support for a hierarchical model of nervous system readiness grounded in polyvagal theory, attachment theory, and sensorimotor approaches to trauma.