[Sciencewoman]

It sounds like you have already made your decision. If that's the case, then contact the adviser. Tell her discretely what you were told, which is secondhand information. Or, just tell her that new information has come to light and you would like to withdraw your rec. Ask her to handle this discretely, without hurting the chapter members' feelings. I'm assuming this may be a WRC; your sisters don't need to hear that a PNM was putting them down. Protect your sisters from the hurt feelings you've experienced.