Okay - why can't a threesome be an HEA?
It IS Ward and we know that there are two characters that are "unconventional" as Ward put it in her words regarding their HEA and their sexual appetites.
Mr. O was killed by Bella. He's the one that tortured and tried to "possess" Bella. We also saw that the Omega "enjoyed" him. And we've seen that the Omega can bring a particular lesser back if he chooses to.
ETA: Also, she has talked about how it's possible for there to be more than one mate. So...Qhuinn has two mates, Blay and a female. I could really see her going this route.