The first is that Jaina loves to plop herself in Sylvanas' lap via blink or portal, and Sylvanas definitely enjoys it (A Recurring theme hngggg >\\\\<)
The second is that Sylvanas accidentally dies at the hands of our very own Archmage (A freshly mana bomb charged archmage is a deadly partner in bed apparently xDDD)
UPDATE:
Yisss you are correct and with the addition of Jaina overwhelming Sylvanas' whole being with her mana. (since Jaina was still "freshly bombed" xD)... so yep, death by orgasm xD