Since town npcs get increased health, but not really, (the game shows me theyre at 1500 / 250 life) the nurse keeps throwing her healing items at herself, which then don't do anything. I guess they don't heal because her hp are above 250 (the vanilla max health)...
Healing / regen doesn't seem to work for any npc above their vanilla health, it's just very annoying with the nurse

Update: Nurse tries to heal herself even at full health