I got this info from:
http://suetonius.blogspot.com/
Its gives the argument that dfm gave, and an argument against that argument
[Agrippina's legacy]
The politically powerful woman would always suffer a devastating ‘image’ problem in ancient Rome, which could be compensated for only by consummate skill in political manipulation. This Agrippina did brilliantly as the wife of Claudius, but tragically failed to achieve as the mother of Nero…
Syme often argued that Agrippina, and other powerful imperial women, were weighty figures in their own day but were essentially unimportant, since they passed from the scene without any lasting impact. This is surely to under-estimate Agrippina's significance. She represents an essential stage in the evolution of the imperial system, in the attempt to give a formal definition to the political role open to a woman of ability and energy. She did not change the hardened attitudes of her contemporaries, but she did define what Romans were willing to tolerate. Her experiment may have been a failure but it was not without its long-term effects.
It can surely not be a coincidence that she was the last woman to play a dominant role in Roman political life for a century and a half. Later generations of imperial wives and mothers who might otherwise have entertained aspirations to power clearly took to heart the bitter lesson that Agrippina learned when, in 59 AD, she was beaten and hacked to death by her son’s hired assassins.
