what do i do about the workplace bullying?

i work with a friend (who now hates me) and appears to be turning everyone against me. i got her hired a while back and since being hired she never once completed a full work week. she always texted me about reasons she may be calling out etc. which always let me down because then it wouldleave me the only nurse to cover the floor. so i went to my boss and asked if i could switch my days around without telling her why. the next day this coworker calledout without speaking to our boss or anyone directly. she left the building without a nurse until my boss woke up and saw the text. i had to rush in on my day offto cover the floor. my boss then told me she was cutting this coworkers hours and told me she was putting me in the hours because of my reliability. this has caused so much animosity at work and now this coworker is turning everyone against me.