I believe that she was using the term "linear" in the computational/signal processing sense, not that of computing.

In electronics, in a linear system, you can decompose a complex waveform and analyze its response to each frequency discretely, and when you recompose them, you get a correct answer.

In a non-linear system, such as a mixer, no such analysis is possible, you have to consider all of the frequencies, and their levels at the same time.

Also consider that most algorithms are founded on a deterministic computational method.

I believe the point is that quantum computers allow you to manipulate a linear combination of bits, whereas simulating the weather would require non-linear combinations. It's unclear how a QC would help simulate something like that better than a classical computer.