She’s also Mrs BAAL as well as being his sister.
ANATH caused a lot of hassle by wishing to appropriate a very special bow belonging to a mortal called Aqhat. Being a bit of a bitch, she zapped him to the Underworld, but he wouldn’t let go of the bow and it went with him.
This caused no end of problems as it was actually a sky bow which held up the Heavens. So the sky collapsed and ANATH had to eat humble pie and ask EL to sort it all out — partly through embarrassment and partly because she was going bow-legged under the weight of the sky.
She then appears to have emigrated to Egypt under the name ANAT.