If angered, she could simply express her grievance through communion with her ancient lusus of the deep, and turn its psychic devastation on her multitudes. The class hierarchy played into her hands politically in this respect. Killing off a haphazard swathe of the population, or an entire class, was suitable as a measure of last resort, but mass extermination does not lend itself well to practical governance. Its looming threat however is quite effective, especially while her empire was partitioned neatly into blood castes. She could use her leverage to delegate oppression to the subjugglators, whose unique abilities and exceptional brutality made them natural enforcers. They too would delegate in their governance, exploiting the pride and loyalty of dangerous bluebloods beneath them, and so on down the hemospectrum, until the enslavement of the common castes was inescapable, in spite of their genetic gifts and strength in numbers. As a self-governing body, the land dwelling portion of her empire was formidable. But her force of sea dwellers was equally formidable, and the two were kept in check not only with the threat of psychic annihilation, but their mutual hatred and distrust.
The only threat to her power was unification through uprising, a possibility made remote once she fully decentralized the race from the homeworld. She scattered all but the children throughout the galaxy after the most recent rebellion led by the Summoner. Upon doing so, she became so comfortable with her grip on power, she risked venturing deeper into space than ever before to grow her empire.
But the more space she put between herself and Gl'bgolyb, the more she risked weakening her bond with the monster. The bond she and her successor shared with it exclusively could sway, and become strengthened with the younger. Perhaps she grew complacent with the threat successors posed, after such a long history of killing them with ease. Heiresses upon reaching maturity were expected to challenge the Condesce for the throne. It was not merely expected of them by their people, but demanded by their shared lusus.
I like to think of her as the pet I gave to their race, at the dawning of their species' evolution. Like a sentience-warming gift. Again, it's just the sort of thing a good host does.