The Tartan Hearts, who beat Wales 1-0 on Sunday and 5-2 on Monday at the same venue, were 2-0 behind at half time in the final game but responded to secure a seventh win in their last eight games.
Head coach Chris Duncan said: “It is not easy to go two goals behind and come back to win and it speaks volumes of the players.
"We made it tough on ourselves but we showed a different side of ourselves and, having pulled it back to 2-2, it was great to see us not settle at that. We didn’t come here to draw and out of all the wins we’ve had recently this might be the one I’m most proud of.”
Scotland thought they had opened the through Watsonians star Sarah Jamieson but the shot was judged to have gone wide amid claims that it appeared to have gone through a hole in the net.
The incident knocked Scotland off their rhythm and Wales finished the first half 2-0 up.
They pulled one back early in the third quarter when Jamieson took the ball on the right, beat two players then picked out Bronwyn Shields, who flicked the ball over the goalkeeper into the roof of the net.
Scotland equalised when a penalty corner was deflected home by McKenzie Bell and Robertson, who was impressive throughout, sealed the win when she converted a rebound.