Yu Lin Bloodhawk certainly could not tell Onyxia why he knew where her lair was, but saying nothing would only cause more trouble. This female black dragon would never stop pursuing an answer, so he could only invoke Quel'Thalas and let her assume that the information had come from its intelligence service.
"All right, I'll find you a room. Space aboard is limited, so I'll have to rearrange things. Wait here for a while." Then he looked at Sylvanas and said, "Could you be a little friendlier to other people? At least don't get into a fight, all right?"
"I have no interest in arguing with her," Sylvanas said.
Then why did you start arguing the moment you met? Yu Lin Bloodhawk looked thoroughly unconvinced, but he still got up to arrange a cabin for Onyxia.
It did not take long to find Onyxia somewhere to stay. When Yu Lin Bloodhawk returned, he breathed an inward sigh of relief. Fortunately, these two violent women had not clashed while he was gone, though the atmosphere was hardly pleasant.
Sylvanas continued sipping her tea elegantly, while Onyxia gazed at the scenery around them. Neither spoke, each occupied with her own business, but as Yu Lin Bloodhawk approached, he could still feel the tension.
Yu Lin Bloodhawk really wanted to say something to ease the sharp conflict between them, or at least change the atmosphere, but even after racking his brains, he could not squeeze out a single word. In the end, he simply stayed silent too, sipping his tea and waiting for reports from the front.
To be honest, Onyxia had caused him considerable trouble, particularly during the most recent battle against the centaurs, which had forced him to send his troops back to Ratchet and take their current sea route instead.