Why did boudicca hate the Romans?

Because Boudicca and the Romans had a difference of opinion. Her husband was a client king of Rome and living under Roman law. When he died he willed half of his kingdom to Nero, the Caesar at the time, and the other half to his wife. However because of Roman law a woman could not inherit,(except for a small restricted amount) from any husband or male relative. When Boudicca went to try and claim her inheritance, it was denied, she got nasty and so did the Romans. They flogged her and raped her two daughters.