Valérie Trierweiler has been quiet since losing her role as France's first lady earlier this year. A tweet from her now is causing a storm as former partner François Hollande visits Mexico. Her tweet draws attention to a custody battle involving Frenchwoman Maude Versini and one of Mexico’s most powerful politicians Arturo Montiel. Trierweiler urges Hollande to act. However, the case is sensitive - Montiel is the Mexican president's uncle.