Note: This is not a feature request for Wanda to be healed when she is wearing the red amulet.
Wanda gets her hunger drained whenever her age is not 20 and she is wearing the life giving amulet, the game thinks that her "health" isn't full and therefore tries to heal her. This wastes both her hunger and the amulet's durability. Although not many people would wear the amulet always, this is probably a minor oversight in my opinion, unless this is intended.
1. Wait for/Set Wanda's age to be 21 years or older. (20 would make the Amulet work as intended; not healing the player.)
2. Wear the Life Giving Amulet.
3. Wait it out, and you will see that her hunger gets drained and nothing happens to her age. The amulet also loses one use.