What happened to her?

As a genin, she was on a team lead by Orochimaru, who became strongly interested in her. He taught her some of his signature jutsus, and (in the anime) even his knowledge on immortality. Orochimaru later tested his Curse Seal on her, and out of the 10 other test subjects, Anko was the only survivor.

After that, Anko refused to follow him anymore but he didn't want to kill her because she was a valuable research subject. Instead, he altered Anko's memory to make her believe she'd been abandoned because she couldn't fuel the cursed seal. Which lead to her having a grudge against Orochimaru for his actions and she believed that as his former student she was responsible to stop his crimes.