I do agree with you in the sense that she was an evil woman, though she is considered a saint in the Orthodox Church beleive it or not, (I was shocked), and you do have to admit that she did bring much stalwart support behind her husband, she did bring in new reforms and changes in public policy and helped make women more equal, (though they were still not of course), than they had been in the past and had it not been for her steadfastness in the face of the Nika revolt, Justinian may not have held the throne.
Have you also heard of the theory she had Theodoric's daughter Amalansutha killed by her cousin because she felt threatened by her? Essentially, Amalansutha had good relations with Justinian, perhaps very good relations and Justinian, it is claimed, took a liking to her since she was of such noble birth and was educated like a Roman and good speak of the Law Codes and Administrations in Latin or Greek, so Theodora, being nothing more than a Circus Performer felt threatened and had her killed. When Amalansutha's cousin had her arrested, Justinian said he would take action if she were not placed back on the throne, yet the cousin recieved a secret message from Theodora telling him to get rid of her and that she guarenteed Justinian would do nothing. After her death, Justinian used that as his pretext to invade Italy. You can throw the theories either way but an interesting one to think nonetheless.
I have no idea...