@chevan
She was growing mold, not microorganisms. They can still use "mold with some special characteristics" even if they unaware that those characteristics caused by some unknown microorganisms.
She said that paper was very detailed, most probably it contains many details how to identify the mold that they require.
P.S. Also, since there were already quite some time after the invention of microscope, as a researcher, she definitely checked with it her "previous works", so she might even recognize the form of bacteria itself.