According to the Italian Wikipedia article, there were two Laudomia de Medicis. This is the younger Laudomia who married Marshal Piero Strozzi in 1539, moved to France in 1548, lost her husband in 1558, and died in 1559. She looks very young for her age.
There are several versions of this portrait on the Internet. The version I used, from Wikimedia where it is called Isabella de' Medidi, had blue-colored flaws over much of the background and a strip in the lower right of her skirt. The background was re-colored and the strip in her skirt was re-colored using nearby parts of her skirt for the color with Photoshop. Is abella de Medici was portrayed wearing a similar dress, as seen here.