Kenny Chesney could’ve looked in his own backyard and found a gritty-voiced younger woman to star opposite him in “Me and Tequila.” Bonnie Bishop was here all the time. She played the Texas scene early on, but eventually made the move that fans there tend to consider selling out, but plenty of people in these parts see as perfectly sensible: She came to Nashville in pursuit of songwriting success. It took a few years, but good things began to happen. Another Bonnie — Raitt, that is — cut an eloquent regret ballad that Bishop co-wrote with Al Anderson. And Bishop returned to doing her own thing with newfound verve. On her new album Free, she sounds like the gospel-fired sister of Grace Potter. Of the two of them, it could be argued that Bishop’s drawing deeper from Janis Joplin’s blues-shouting, rock ’n’ roll well at this point. But the redemptive lift of Bishop’s latest songs strongly implies there’s no need to fear she’ll meet a similarly tragic end.