Why did Ismene object to the burial of their brother Polynices?

In the Greek tragedy "Antigone" by Sophocles, Ismene does not object to the burial of her brother Polynices. In fact, she is initially supportive of Antigone's plan to bury him, despite the risk of punishment. However, when she realizes the potential consequences for both herself and Antigone, she becomes fearful and tries to dissuade her sister from going through with the burial.