NEW YORK (AP) — Score one for JetBlue in the dogfight over who gets to buy Spirit Airlines. A firm that advises investors on proxy voting said Tuesday that Spirit shareholders should oppose Frontier Airlines’ bid to buy Spirit, saying that JetBlue has made a better offer. Institutional Shareholder Services says both bids carry the risk of being rejected by regulators, but JetBlue offers a $200 million breakup fee if that happens, and Frontier does not. The advisory firm says Spirit shareholders should reject the Frontier offer to signal its board to negotiate further with JetBlue. Shareholders of Florida-based Spirit are scheduled to vote June 10 on whether to approve Frontier’s stock-and-cash offer.