When we would select our Rho Chi's, they would disaffiliate completely from the sorority until bids were distributed. It was very hard on them. One day I was wearing letters and saw a sister of another sorority who was a rho chi. She said that she couldn't hang out with anyone in letters even if they weren't hers because it might influence the rushees. The rho chis didn't attend their chapter meetings or dinners or anything. They all hung out with each other. I never heard of any of the problems that you are experiencing. I guess that I was lucky.
The rho chis shouldn't report back to their chapters what the PNMs said about them because it could definitely affect the outcome of the recruitment process.
I figure a rho chi is like a priest, and anything that a PNM says during rush is confidential. 