How should I handle my dysfunctional sister?

The problem is my sister has stopped talking to me again. When her life is in order, she cuts me out. When everything falls apart (which it often does, because she has these narcissistic drama tendencies), she will call me 5 times a day to get her through her suicidal thoughts, want to talk for hours, send presents to my children, and be more involved with the entire family. It’s exhausting. I know that this behavior is a product of our dysfunctional family, and that she is getting psychiatric help, but this same pattern persists between us year after year. She just had a baby. I can live without talking to her, but there’s this new baby, and what about when it all falls apart and she starts calling in tears again??