[@RomanAria]
I took the leisure to compile some resources that might be useful.

These are the major sources on Locusta.
[url=http://www.perseus.tufts.edu/hopper/text?doc=Perseus:text:1999.02.0078]Tacitus[/url] (Annals 12.66 and 13.15), [url=http://www.perseus.tufts.edu/hopper/text?doc=Perseus:text:1999.02.0132]Suetonius[/url] ("Life of Nero", 33 and 47), and [url=http://penelope.uchicago.edu/Thayer/E/Roman/Texts/Cassius_Dio/home.html]Cassius Dio[/url] (61.34 and 63.3)

Also, from what I can see, it might be interesting to superimpose Medea's character on Locusta.  This [url=http://en.wikipedia.org/wiki/Medea#Primary_sources]link[/url] to Wikipedia has a list of the works that Medea appears in.  Of all those sources, I would recommend Euripides' [i]Medea[/i].  While it is a Greek Tragedy, it probably is the most well known depiction of the character.  If you need a link to Euripides' [i]Medea[/i], just let me know, although I bet you could find a copy at your local library.

Other authors you should look at are Ovid and Seneca.  Seneca actually has [url=http://www.theoi.com/Text/SenecaMedea.html]his own version[/url] of the [i]Medea[/i].  The nice think about Ovid, Seneca, Tacitus, and Suetonius is that all their texts are in Latin, so if you find something in them that you like, you can look up the Latin and try to imitate some sections or descriptions.