Sigh. Another Gravity Realism Question.
I'm kidding of course. I was caught out by this attitude when I posted my own question about the Physics of the movie.
As much as you'll want a decent answer to this, it's likely that the only one you'll get is the same as mine; the film is hugely flawed, scientifically speaking.
I'll refer you to the link Christian Rau was kind enough to provide me with, from a real life astronaut fact checking the movie. He addresses this question in his interview.
Actually, I really couldn't understand the tension there. Sandra has her leg caught in some parachute rigging, and she's holding on to George by his hand. I think all he would have needed to have done would be to crawl up on her, and basically rope-climb up toward the space station. Or just lightly pull and he could have flown himself up to the space station. There would be no continuing motive force to continue to pull him away. So that physically didn't work for me.