Would the Spiritual Guardian feat from ACG apply to (using the line "or a similar spell that grants you a spiritual guardian") the Guardian Spirit you gain from the Summon Guardian Spirit feat that adds the monster to the summon monster/nature's ally spell? The shaman in question has the Friend to Animals hex of the Nature Spirit in order to cast summon nature's ally.
Spiritual Guardian: http://www.d20pfsrd.com/feats/general-feats/spiritual-guardian
Summon Guardian Spirit: Monster summoner Handbook pg 26
Guardian Spirit: http://www.d20pfsrd.com/bestiary/monster-listings/templates/guardian-spirit -cr-varies
