Sorry to say this that I dont think it was Mariamman who possessed your aunt .As you mentioned in you story she spoked both man and woman’s voice.No Hindu Goddesses demand they want 20 chickens.Please remember that Mariamman will be angry if your aunty has spit in front of the temples as even you are from diffrent religion should learn to respect other religion.But I dont agree that Mariamman ask for your aunty’s son’s blood.This is absolutely rediculous.