Then let form drawing rest for a while. Do none for a time. When you judge the time is right, spend some time talking about the forms in nature that you two drew and then perhaps let her look through your form drawing book for a for a form that reminds her of the water (or leaves). Let her copy it - and if she's still being a tricky customer, let her copy it directly out of the book - otherwise, I'd suggest you do it in the usual way with you drawing it large on the board and then her copying. Maybe recite a verse about water or leaves while she works - (though some children would prefer not to have a verse, would prefer to remain in the memory of what they experienced in nature) let her work with it in her own way. This might just help break any stalemate that could be forming over this issue between you two. And, assuming all goes well (??!!!) you can see what to do next - "Here's a more complicated form - let's try this".