Gallia is at their furthest extent. As others have pointed out, they're stretched way too thin and fighting on too many fronts to have a chance at victory now. If they were smart, they'd try for an armistice, pull back to Tau-31, and redeploy their forces back home to deal with the Council and Maquis.
When the LN and BAF succeed in turning back the Gallic advance, Bretonia is going to owe a huge debt to Liberty. It'll be repaid both in direct payments as well as lucrative trade deals for Libertonian corporations. I wouldn't rule out a permanent Libertonian military presence of some sort, perhaps a base or something, even. Bretonia is going to take a long time to fully recover, and Liberty will cash in.