I'm wondering about the container size too. If this plant is basically the property of your cat, I would not want the container to have too much exposed potting mix which the cat begins to use as an alternate litter box. If so, then large pebbles over the exposed surface would be called for.

If your plant goes from a south facing balcony a few feet inside the window also facing south, little change of its environment, unless there is a heating vent blowing on it.

I've never kept one indoors in a container, but grasses are pretty hardy plants and even look good planted in a bird bath to simulate a water feature....which requires regular watering. However, mine planted that way died, so I'm no help telling you how to keep one alive!