A nice bit of casting. Sounds like she is a major character as well; the below is from comicvine.com.
Marvel announced on their website today that Rosario Dawson (Sin City: A Dame to Kill For) has signed on to join “Marvel’s Daredevil,” the 13-episode series which will premiere on Netflix in 2015 as part of a new Marvel initiative to put their character’s on the small screen.
Dawson will be playing a young woman trying to make things better in Hell’s Kitchen which brings her and Matt Murdock into her life.
“Rosario Dawson is one the most charismatic, talented and powerful actresses in Hollywood, so she was always at the top of our list for ‘Marvel’s Daredevil… Her role in the series is absolutely critical to Matt Murdock’s journey to become the hero we know as Daredevil.”