However do you tell a friend they are ill? How do you tell someone to get help?

I have an aquaintance who seems to be droping further into illness. I have grown convinced her beliefs that both her employer and union are persecuting her are paranoid delusions. I have tried to support her in this but there comes a point that you can't any longer.

She still needs support and friendship but I don't want to further encourage her delusions. How though - is there a gentle way - do I tell her she needs psychiatric help?