I doub that Arya has the skills to take down the Waif 1v1 unless luck is involved or she has an ace like coating needle in poison.
I'm guesing that Arya will probably lose but she won't die. The fight will leave her close to death where she will be rescued by some unexpected character. It could be another House of B/W defector or someone we've already met from the playhouse.
Then again, Waif does have her weaknesses. She's personally involved, arrogant, and she underestimates Arya. She'll want to confront Arya head on and with plenty of time to monologue. These faults could lead her to making a mistake during the fight.
It's interesting that the Waif is as obsessed with ending Arya as Arya is with ending the names on her list. The whole episode will teach Arya the pitfalls of assasinating a personal target. How it can leave her blind.
As for the chase scene in the preview, it's either Arya running for her life or Arya leading the Waif into a trap.