AIUI, the French high command in 1939 was not prepared, psychologically or organizationally, for offensive war. They accepted that they would do it - eventually, when the time was ripe, when all preparations were complete. They had expected the German conquest of Poland to take at least several months to a year. In the meantime, France would complete the mobilization of its army, deploy strong forces in Lorraine, and only then attack.
The swiftness of the German advances in Poland came as a shocking surprise. Obviously the Germans were much more dangerous than predicted. Also, forces that had been expected to be tied down in Poland were moving to the west. France's mobilization process was... a bit leisurely. It was easily a month before all the divisions were up to strength and fully ready for action.
By that time, German reinforcements were pouring into the western front, and the "big advantage" was slipping away. A strong French attack might have broken through the initial front, and possibly pushed the Germans back 50-100 km. But French forces were not organized to sustain longer advances, even German resistance collapsed.
Another point is that (IMO) the Germans would have had air superiority over the battle zone. The French Air Force lagged in numbers, and was still making frantic efforts to catch up in spring 1940. Also, lots of its aircraft were misdeployed: every local command in the country had its own little interceptor force. The larger and far better organized Luftwaffe would dominate (though the French would still be a presence). The RAF could help, of course, but I don't see many squadrons being assigned to Lorraine.