A 65-year-old woman died Saturday following a head-on collision in Wellfleet, according to police. Authorities responded to the accident at the intersection of Route 6 and Old Truro Road at 6:18 p.m. and found Sharon Sullivan of Eastham in critical condition, a statement from the Wellfleet Police Department said. Sullivan was taken by helicopter to a Boston hospital and pronounced dead upon arrival, according to the statement. The driver of the other vehicle, Virginia Souza, 83, and the passenger, Manuel Souza, 88, both of Truro, were taken to Cape Cod Hospital, the statement said. An initial investigation determined that Sullivan was southbound on Route 6 when her vehicle crossed over into the northbound lane, striking the Souzas’ car, police said. The accident is under investigation by Wellfleet police and the Cape Cod Regional Accident Reconstruction team.