re: What do you think Arya's new weapon is foreshadowing?

Ice was split into Oathkeeper and Widow's Wail.

Tywin gave the blade that came to be known as Oathkeeper to Jamie, who gave it to Brienne, who named it and still has it.

Tywin gave the other blade to Joffrey at his wedding ceremony to Queen Margaery. He named it Widow's Wail. Then he died.

When Jaime was in the room with Olenna at Highgarden, she asked him if he was wearing Joffrey's sword. He said yes. She asked him what Joffrey named it. He said Widow's Wail. She asked him if he was going to kill her with it. He said no.