It would seem that others in her crew figured it out:
Vin frowned. “Camon was an Allomancer?”
Kelsier shook his head. “He must have admitted to something heinous during his torture.” Kelsier glanced at Vin. “He must have known what you were, Vin. He used you intentionally.”
She paled slightly. “Then . . . the Ministry knows that I’m a Mistborn?”
“Perhaps. It depends on whether Camon knew or not. He could have assumed you were just a Misting.”
The Final Empire - Chapter 11
And Reen knew who her father was:
Vin clinched her teeth, then forced herself to relax. “I saw my father at the ball tonight,” she said, hoping to distract Kelsier and the others away from Lord Venture.
“Really?” Kelsier asked with interest.
Vin nodded. “I recognized him from a time [Reen] pointed him out to me."
“What is this?” Renoux asked.
“Vin’s father is an obligator,” Kelsier said.
The Final Empire - Chapter 13
And he worked very hard to keep her from the attention of the Inquisitors:
Reen was not a good person. He beat Vin, he was selfish, and he was conniving. However, he did love his sister. Most of his beatings happened because he was worried that she would expose them somehow and get herself killed. He knew that the Inquisitors were chasing her because of her half-breed nature, and so he uprooted them constantly, moving from city to city. He kept her alive, teaching her to be harsh, but teaching her to survive.
Annotation - Mistborn Chapter 37 Part One
(all emphasis mine)
So did Reen ever know or suspect Vin was anything other then a simple half-breed? If so, did he know she was a full mistborn?