She was at 9-under 207 entering Sunday's final round, with Annika Sorenstam, Laura Davies and Veronica Zorzi at 208.
Sorenstam, seeking her first victory this season in a year marked by injuries, had a bogey-free 68. Davies had a 71 and missed a chance to take the lead with a triple bogey on the par-5 13th. Zorzi shot a 70.
Louise Stahle, the first-round leader after a course-record 64, was at 211 after a 73. Lisa Hall, the second-round leader made two double bogeys for a 77 and dropped to 213.
Tinning, winner of the Ladies European Tour Order of Merit in 2005, had no expectations for Sunday's round.
'I'll just try and go out there and make as many birdies as I can,' she said. 'There are some fantastic players right behind me, so it definitely wont be easy.'
Sorenstam said she benefited from making a minor change to her swing after talking with her coach, Henri Reis.
'I have to keep fine-tuning my swing after the neck injury. I was just trying to keep my shoulders square and hips slightly more open at the point of impact,' Sorenstam said. 'I was quite pleased with my round and I feel like I hit some good shots. I feel like I've still got some work to do, but I'm hitting some good shots and that's what matters.'
Davies made her second eagle in three days on the par-5 third hole, but the triple bogey on the 13th disrupted her momentum.
Sophie Gustafson looked set to win the Order of Merit title. She was second on the money list behind Bettina Hauert and was at 2 under for 12th place in the tournament. Hauert shot an 81, putting her in last place.
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