After England beat the Netherlands 4-0 earlier on Wednesday (Thursday AEST), France went top of the group on six points, followed by the English and the Dutch on three points each.
Wales, who face England in their final group game on Sunday, have yet to register a point but still have a mathematical chance of making the knockout stages.
France face the Netherlands in their last group game.
Clara Mateo was at the centre of much of France's attacking play in St Gallen and lashed them into an early lead, controlling a flick-on from a corner on her chest and firing a volley into the net in the eighth minute.
The moment thousands of Wales fans had been waiting for came five minutes later when Ceri Holland broke down the left and, though her first attempt to find Jess Fishlock was blocked, she managed to steer the ball to the 38-year-old, who poked home Wales' maiden goal at the Women's European Championship finals.
Wales looked set to go into the break level, only for Holland to chop down Mateo in the box. Kadidiatou Diani's spot kick crept over the line after striking the foot of keeper Safia Middleton-Patel.
Just after the break Middleton-Patel lost control of the ball in the box, allowing Mateo to tee up Amel Majri, who scored.
After that the Welsh wilted, with Grace Geyoro scoring France's fourth in the 63rd minute to crown a convincing win.
In Zurich, England's Lauren James scored twice, while Georgia Stanway and Ella Toone also found the net to give the defending European champions an emphatic 4-0 victory over the Netherlands.
Four days after a lacklustre 2-1 loss to France, England came out firing in front of a festive crowd that included Prince William.
James put England ahead in the 22nd minute when goalkeeper Hannah Hampton picked out Alessia Russo with a stunning long ball. Russo slipped it to James on the edge of the box, who worked the ball onto her left foot before unleashing a screamer into the top corner.
Stanway doubled England's lead seconds before halftime, fizzing a first-time shot past wrong-footed goalkeeper Daphne van Domselaar.
An unmarked James completed her double in the 60th minute, and Toone added more misery for the Dutch seven minutes later.
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