Best performance wasn't Rodriguez's or Taylor'
It was easily Mickey O'Hagan's Dinah. [spoilers ahead]
I found Rodriguez to be all ticks and mannerisms, and throughout the entire movie you can't see her face (until the end, in the laundromat). She was "bitch" this and "bitch" that and on and on. Kinda one note. As for Taylor, I thought she was better but played her role as kind of a doomed queen. I think they got the noms they did because they were the leads and "brave." (Read all the reviews that refer to the movie or to them as "brave.") While certainly it takes gumption, I'm not sure what is "brave" about making this film, in that it has name-backing.
It's O'Hagan who steals the show. She takes a really thankless role of "background colour" and runs with it. She's a de-glam'ed sex worker overpowered by the railing Sin Dee, and she conveys an aura of being trodden upon her whole life. She's mousy, but she knows how to play mousy in order to survive. She's sad, but not pathetic. On the bus, she gets some of the best lines as she guffaws at Sin Dee's agenda, and again at the donut shop. She's an addict for whom this life is all she knows.
The end, when she goes back to the hotel, has to be one of the saddest scenes in any movie, similar to Tralala at the end of Last Exit to Brooklyn. She's denied entry, as if it were an unpside-down send-up of Mother Mary and her family being told that there's no room at the inn. (It's a Christmas movie, remember.) When she's told to just hang, she stands there as the door closes, forlorn but with no awareness of what her options might be. She could be standing there forever.
Just a stunningly powerful role. I hope we'll see more of her.