I guess you're right, Heraklia, there's not much about Octavia on the net. Here are something that I managed to grasp about her, in a biography of Augustus:

As you said, Octavia's date of birth is unknown, but believed to be in 69 BC. She married Gaius Claudius Marcellus in 54 BC, so when the series "technically" begins (52 BC) she was already married to Marcellus, a man of the influential Claudian family. They had three children: two daughters both named Marcella, and a son Marcus Claudius Marcellus, who married his cousin Julia (Augustus' only daughter) at a very young age and died not much later. According to Tacitus, the death of Marcellus (Octavia's son, and Augustus' nephew AND son-in-law) could have been planned by Livia, Augustus' wife. Here begins all of Robert Graves' "thesis", so masterly portrayed in his book "I Claudius".

Octavia's husband Marcellus died in 40 BC and not much later, Augustus asked her to marry Mark Antony in order to seal their political pact. Actually, Augustus asked the Senate a special license for Octavia, since she was officially still mourning for her husband, and could not marry yet. Of course, the Senate obliged.

The HBO Rome character "Glabius" is purely fictional.

It would be great if you, Heraklia, could give us a good Octavia website. I, for one, would be a voracious reader!