The ending scene planted a doubt... (spoilers)

In the end, KO has a vision of her sister just before going into the fight. It felt like her sister's spirit was giving her the reassurance that she had avenged her. And with that, KO could have closure and live her life.

But then, why the flashback of her back in the room where she was shot bleeding on the floor? Was that to imply she died in that house? In the earlier scene there were sounds of sirens which indicate that rescue is coming. But that ending flashback made me wonder if she died there and the rest of it was her dying dream?

BTW I really liked this movie, the gritty and raw crime thriller. Any other movies with this vibe? (Run with the Hunted was another)