How much to give your helper for ang bao for Christmas and new year?

No hard and fast rule! Depends on your relationship with your helper and how much you value her. I would probably buy her a gift in Christmas. Say a nice lipstick or a hand cream (something that can boost her self-esteem or make her feel pretty). As for ang bao probably $10 or $20 as I will not wish our relationship to be based on money as much.