What would you do?

I have a close friend who recommended another friend of hers to do some work for me on my flat. The work was finished to an acceptable level but I did not receive the correct guarantees and building reg certificates I should. I asked for them repeatedly but I was lied to and later found out he was not affiliated to the bodies he said he was. So now I have pay the lea for a retrospective building regs cert.

My friend knew I did not have the paperwork but believes her builder friend when he says I don't need them.

Now she is going to use the man for work on her property I have told her he cannot give her the correct paperwork but she still thinks il wrong and he's right. Apart from being hurt by her attitude. I don't Want to see her with my problem. She thinks it will be alright because he displays the trust mark logo on his letters although he is not a member. I have told her to be careful but she thinks I'm wrong and gets angry with me. should I try to tell her more I value her friendship. Or should I leave it