Diona are actually 3 woodlice in a bark suit, therefore the following clarifications of various rules have been made:
Diona Nymphs are to be treated as station pets akin to Ian, Renault, or Smile by the crew or its inhabitants, whether they are sentient or not. When a Diona splits into nymphs, its Brain Nymph remembers its past life before falling crit/unconscious, but is aware that it has died. On MRP the new life rule remains in effect for the diona through all life stages. Other non-brain Nymphs do not remember anything from their prior Diona state should they become somehow sentient. A Diona is only an antagonist in any stage of its life cycle if the game tells you that you are.