Any other body/stunt double in any other film wouldn't be complaining about anything because they understand their job. It's just the fact that Natalie Portman did such a great job in the film. Sarah Lane is just coming across as bitter and desperate.
Anyone with a brain knows Natalie didn't do ALL of the dancing in Black Swan. She spent a year preparing for a role and she pulled it off. People are acting like no other actor/actress has done it before. Take a look at the prep Angelina Jolie did for Tomb Raider (weapons training, yoga, kickboxing) or what Christian Bale did for The Machinist (losing a shit ton of weight) or what Taylor Lautner did for Twilight (gaining tons of muscle to look good without a shirt) or what Jamie Foxx did for Ray (learning Braille and piano, etc.) . They are actors and their job is to prepare for the role they will be portraying. That is exactly what Natalie did and there is no reason for anyone to be bitching about it just because she won a bunch of awards for it. Sarah Lane especially. She was brought in as a body and dance double, not to be featured as a principal dancer or for Fox Searchlight to go around boasting "HAI LOOK AT NATALIE'S DANCE DOUBLE. PRAISE HER FOR DANCING EN POINTE."
Studios and productions don't boast about extras and doubles. Their job is very specific and most of them seem to be proud of what they do. If Lane wasn't happy about that then she shouldn't have taken the opportunity and let them find another Natalie look-alike out of all the women who auditioned to be extras in the film. Not to mention the fact that this really doesn't matter at this point. Black Swan comes out on DVD/Blu-Ray on Tuesday and Natalie has already won a Critic's Choice, BAFTA, Golden Globe, Independent Spirit, SAG, and Academy Award for the role. Sarah Lane is just blowing hot air to an audience that doesn't really care at this point. The only people this might sway are those who haven't seen the movie yet and/or those who didn't have a brain and assumed Natalie Portman did all of the dancing in the first place.
Complaining about it now won't make you a principal dancer, sweetie. You're just coming across as an attention whore.