What disagreement are the sisters having at the beginning of Antigone?
Antigone wants to bury her brother Polynices' body, as the gods ordain, but Creon has hailed a proclamation which states that since Polynices was a traitor, his body must rot uncovered; therefore, whoever buries his body will be put to death.
Antigone wants Ismene to help her consecrate the body, sprinkle it with oil and bury it, but Ismene fears for her life and Antigone's too; she is not as bold as her sister and discourages Antigone from openly disobeying Creon's martial law.
Speaking of her two brothers' deaths, Ismene says:
Ismene takes on the traditional role of women at the time: quite, submissive--glorified domestic servants:
Nay, we must remember, first, that we were born women, as who should not strive with men; next, that we are ruled of the stronger, so that we must obey in these things, and in things yet sorer. I, therefore, asking the Spirits Infernal to pardon, seeing that force is put on me herein, will hearken to our rulers. for 'tis witless to be over busy.
Antigone is the other extreme: bold, resolute. She even has a bit of a death wish:
If thus thou speakest, thou wilt have hatred from me, and will justly be subject to the lasting hatred of the dead. But leave me, and the folly that is mine alone, to suffer this dread thing; for I shall not suffer aught so dreadful as an ignoble death.