Her options? If she was to avoid Sirius and Remus and apparate herself, she was most likely going to get splinched. But if she was to choose to take the Floo, she had to pass by her two soul-bonded and risk getting caught by them. What would be her excuse then? She couldn't very well say she met up with Voldemort! They'd lock her in the mansion for the rest of her life to keep her safe. She couldn't let them see her. She had to be cautious.