What about a brush for her and a brush for you to use on her? We found it worked with DD1 when she was refusing, now she is learning to brush her own really well. She will do it first, then she knows we have to finish it properly. I found changing her back to the 'my first' toothpaste helped as well, it was so strong tasting. As with a lot of things with toddlers forcing will only make the problem worse, much better approach is through encouragement and persuasion, or small bribery programs like sticker charts.