This post contains spoilers from "Game Of Thrones" Season 7, Episode 2.
Arya's life is one that's been filled with losing family members who she never had the chance to say goodbye to. From her father in Season 1 to her mother and oldest brother in Season 3, Arya has spent her life trying to get back to those she loved.
But one of the most heart-wrenching of those partings was early on in the very first season when she chased away her direwolf -- but that all changed tonight when Arya and Nymeria were reunited. While her brothers Bran, Rickon, Robb, and Jon Snow got to spend years with their direwolves, Arya saw what happened to Sansa's pup Lady and realized that taking her best girl to King's Landing was a death sentence back in season 1.
So she did the only thing she could. If you love something, set it free. Nymeria was left behind to grow up alone in the forests of the Riverlands.
Over the later season, Game of Thrones has also had to sacrifice direwolves. With a TV budget that only stretches so far, they've chosen to put their money into the dragon triplets Dany was raising, rather than the direwolves. Not only was Arya's choice to send away Nymeria a way to save her from the butchers of King's Landing, it also saved her from being killed off on the altar of sacrifice "to the CGI budget."
Arya has now spent the last few years raised by the packs she's joined up with in various places until she grew into an adult and could go her own way. And as she's discovered tonight, Nymeria has too. But unlike Arya, Nymeria has her pack. She's not alone in this world, and she never will be, while she's strong enough to lead these wolves into battle. The lone wolf dies, but the pack survives.
Arya has tried being a lone wolf these last couple of seasons. And while she's survived by luck and skill, heading to King's Landing to murder Cersei is probably signing a death sentence. If she wants to survive, she needs her own pack. Nymeria can't come with her anymore.
Let's just hope they welcome her with open arms when she arrives in Winterfell. She needs them.