I had four possible plans. One was to try to entangle Umbridge with Aragog, the giant spider that lives in the forest, and his kin. While that would probably have taken care of her, the spiders would consider me and Harry just as edible as she was, and without my wand, I couldn't fight back. Another was to let her meet Grawp. The sight of him, I figured, would distract her from us, and she'd probably attack him, which would give Harry and me a chance to slip away. The third was to wait for her to trip over a root or fallen branch, and jump her before she could bring her wand into play. That would have to be a last resort, though.