I thought Romans largely cremated their dead. It would have been helpful had they provided an approximate date for the burial. Maybe she was from a later or earlier era I am most familiar with, the 100 years where the republic sank and the empire began.
Cremation was indeed usual, but not exclusive. Inhumantion was not uncommon, throughout Roman history. There's not some specific era for it. Sarcophagi were used to hold inhumations as well as cremations.
The Roman republic was actually just a hierarchic state run by a hereditary oligarchy. There was no republic -- senators had to be from specific families, and decided when and for how long they'd serve. And even in the sol-called republican period, Rome was already an empire, beginning with the conquest of Ostia. The evolution of governance to add a permanent, full-time chief executive was a necessity, and led to upward mobility among Romans and newly acquired citizens in the various conquered areas. The last of the "old family" emperors was probably Galba, who ruled for a few weeks or months during the Year of Four Emperors.