Refused to sign the contract for Job Offer?

Last Friday while I was having an interview for a job I really didn't like, the company that I was hoping to work for called me for an interview for today. I was hired for the job I didn't like last Friday but did not sign the contract and asked if I could think about it first. They told me that I have to sign it tomorrow (Saturday) which I didn't and didn't show my face. Now my friend wants me to go to back to the office to say that I am not going to take the job (bec she was the one who recommended me and is afraid that it would all reflect on her). I'm so ashamed that I don't want to go there. Need an advice how to do this properly.