When Mistress fled the palace, she also warned the eldritch beholder. If the eldritch beholder followed them to Liguritudum, she would be a formidable ally.
Normally, if a sovereign lost a country but was still alive, the country guardian didn't have the duty to continue following said sovereign. The country guardian was released from his contract and was free to leave. So, unless the relationship between the country guardian and the sovereign was deep, the country guardian most likely left once the country lost.
The eldritch beholder didn't have any meaningful bond with Mistress. She came into Mistress' service out of the agreement for freeing her from Broidrireg's seal. So, rationally, Mistress shouldn't have told the eldritch beholder about her relinquishing her throne because this should just caused the eldritch beholder to leave both her and the country.
