Sayaka was not listening to sense. So be it. Homura adopted the cold attitude of her earlier days.

"I have no plans to do so," she said clearly. This was for Sayaka's own good - or at least, it would be good for Sayaka even if that wasn't exactly Homura's motivation. She didn't bother feel guilty over still putting Madoka first.

Surely, even Sayaka couldn't be so stubborn as to think she could fight without the weapon? It was an act calculated to force her to safety.