Though Anwina is referred to as the guest, I think only little Pamela is truly her guest. The little undead girl came here to look for her "Sister Anwina." She doesn't even know what the Xyrin Emperor means — it was polite enough of her not to ask if the 'Emperor' was edible. As for Aegwen and Medivh, they seemingly want Anwina to introduce them, to find Bubbles...
According to Medivh, he was able to break free from the curse and have another chance at resurrection thanks to Bubbles. But at that time, Bubbles was in a hurry to raid the Icecrown Fortress (I suspect she went to beat up Arthas again...), and he didn't get a chance to thank her. This time, he mainly came to express gratitude and seek a way to restore himself — the latter being a matter of luck. Even if full recovery isn't possible, both he and Aegwen are highly skilled magic experts and will naturally figure something out themselves.
