Seagram heiresses Clare and Sara Bronfman have hit a roadblock in their quest to silence a former pal who exposed their $100 million support of a controversial upstate group described as a “cult.” A California judge has told the sisters he’s waiting until July 28 to decide whether they can go ahead with a suit against their former financial adviser, Barbara Bouchey — or whether he’ll grant Bouchey’s bid to drop the litigation altogether. The move is a setback for the Bronfmans, who want to keep any more financial documents from being made public. They sued Bouchey in February, after she turned over “sensitive” records that revealed their $100 million donation to NXIVM, an Albany-based “self-awareness” group, from 2005 to 2009. The sisters’ dad, Edgar Bronfman Sr., termed the organization a “cult.” The records were turned over as part of a different lawsuit involving NXIVM and a failed real-estate deal.