We know that the first time Natalie set Leonard up to get someone (a thug named Dodd), her motivation was selfish, and she deceived Leonard in the process.

However, when she helps him find the John G. he's looking for, it seems as though she's genuinely trying to help him. Maybe she did it because she felt guilty for taking advantage of Leonard earlier, or perhaps (like Leonard himself guessed) out of pity.

Was Natalie genuinely trying to help Leonard, or was she just using him again the get back at Teddy for her boyfriend's death?

It just seems like too much of a coincidence that the John G. who's license plate she looked up was in fact Teddy, the man responsible for her boyfriend's death.
We know that Natalie knew of Teddy because she mentioned him in the scene where she discovers Leonard's tattoos, saying that her boyfriend went to meet a guy named Teddy and didn't come back.
Another clue is given when she hands over the license plate details to Leonard, when she says she saw the man from the picture in the bar where she works.

However, it is never explicitly said in the movie that Natalie knows that the John G. from the license plate and Teddy are the same person.

Can anyone point to other clues in the movie that can corroborate one of these two views?