I am a caregiver for a friend with terminal cancer. Does Medicare offer a salary for caregivers?

Medicare does not pay for caregiving. Your friend should be paying you from her own assets.

Unless you are doing this out of the kindness of your heart your friend should be paying you and there should be an agreement in place. when will you no longer be able to safely care for your friend? Does your friend know that and is your friend prepared to either hire someone else or transition to a facility that can care for them 24/7?

No