My friend wants to commit suicide by overdosing on protein pills then going to sleep. Can that kill her?

What protein pills? What protein pills are under consideration and from where does the friend expect to procure such pills?
No, inaction will. If your friend is trying to commit suicide, then you're morally obligated to get her help. Call 9-1-1 or get her to crisis. These probably will make her sick, but next time she'll pick a more lethal avenue. She needs help now!