Demona's hatred towards the Kraang can be justified as in addition to some implied history between them it was confirmed that she would see the Space-Spawn in Gargoyles 2198 as an even greater threat to Gargoyles than humanity ever was.
We saw what Dr. Sevarius was capable of in regards to his mutation experiments, imagine what he could do if he had knowledge and access to the Mutagen/Ooze.
