Any plant can be toxic to any cat as they can have allergic reactions specific to just them much like some humans are allergic to peanuts and others are not. I have grown Lirope or Dwarf Mondo grass for years and have seen my cats nibble on the leaves with no ill effects. Mostly due to my own experience I would say dwarf mondo grass is not toxic to cats if they take a bit of a nibble. The California board of poison control lists lirope as non toxic to humans but  there is no mention of toxicity to cats. Keep growing, Marianne Binetti