The convention you are describing (the feminine form of the gens, with a modifier of minor or secunda or whatever), was really traditional and belongs in the Republic. By the end of the Republic, we see a break in this convention. Also remember that the bulk of the names we see are aristocrats, and their conventions tended in all respects to be more conservative.

By the end of the Republic, two names seem very common, especially for women with a public profile. We start to see gens + a fem. form of the cognomen, for instance. A really great example is the wife of Augustus, Livia Drusilla (her father was M. Livius Drusus). In this instance, the cognomen has a diminutive ending. Another convention was the genitive of a husband's gens, like the famous Clodia Metellī. If you look at the Julio-Claudian naming conventions, there is a trend to give women names which emphasize their extended family trees. The daughters of Julia and Agrippa were not Vipsania and Vipsania Secunda, but rather Julia and Agrippina. When Agrippina had three daughters with Germanicus, none of them were named Claudia, but instead Drusilla, Agrippina, and Julia Livilla.

Interestingly, the practice of using simply the feminine of the gens was distinctly Roman as far as Italian civilizations. Etruscan inscriptions, for instance, often show womens' names with a praenomen and even sometimes a "cognomen" (or rather the equivalent). A famous one is the lovely "Seianti Hanunia Tlesnasa." It just rolls off the tongue.