I also say the pic is not a great shot for telling gender. It really could be the cord there.
That said, I found out with my first son at 13 weeks. I got a perfect potty-shot and it was fairly obvious he was a he. So I don't think 12 weeks, 5 days is "too" early for a guess. Although i would not paint the nursery yet. I think boy guesses are a little more accurate than girl ones at that stage. The tech also got lots of shots that were not printed out, so if she is any good (or has been working as a tech for a long time), I would be inclined to think she saw what she said.
Good luck...update when you find out for sure