My son does the same thing. Honestly I've never really thought much about it and just draw what he asks for. He does it mostly when we color or do side walk chalk. If we're doing it on paper I usually get a separate piece to draw my things so I can keep his art separate. When we paint he doesn't seem to ask me to do anything so maybe a different medium would allow her to focus on just the flow and movement of color rather than drawing concrete things?