I'm certain this isn't something only I do, but I always assign theme songs to basically every major character I write, based on lyrics, the tone of the songs, the title, etc.
This one is Lee's and believe me, she has a few, but this is the one I consider the most fitting.
If you want the full range, see also Ophelia by Natalie Merchant, Gun by CHVRCHES or Bulletproof by La Roux.