Her preferred drawing implement is the ball point pen and, in my opinion, she's developed a very distinctive style. I've included some samples of her work below. She likes to cover a surface with these tight little scribbles, then pull
them together with a few big ones. Sure I'm biased, but I find them quite compelling.
Each one of these little hieroglyphs apparently represents something as well, as you can see in Alisa's annotated example. Alisa asked Oliva, "what's your drawing about?" and came back with all sorts of subjects like ice cream and backpacks.