So Undercover (2012) on Netflix

Molly Morris is a private investigator based in Dallas and one day F.B.I. agent Armon Ranford offers her a job with the F.B.I. to watch over Alex Patrone, a senator's daughter, who was involved in an organized crime case. Molly accepts the offer and goes undercover as a sorority student named Brooke. She meets Sasha , the head of the sorority and other members esp Alex, whom she has been hired to protect. Molly also meets Nicholas, another student at the college and falls in love. Molly begins to suspect Professor Talloway when she discovers that Alex secretly goes off to his lake house. She reports back to the FBI, (who at one point tells her that Nicholas Dexter has a fake name which she doesn't believe). Things get even more complicated as people turn out to be not who they say they are and suspicions fly in every direction.