The 40-year-old Columbian actress got engaged to her businessman boyfriend in July this year and Loeb, 37, recently went behind her back and fired members of her support staff, reported Showbizspy.
Loeb has also reportedly been pressuring Vergara to make questionable investments as well as alienating her from close friends.
"Nick is a very controlling guy. He fired Sofia's beloved maid a few weeks ago. He warned Sofia's handlers that her manager is on the chopping block too, because Nick wants to push her more into movies and away from TV," a source said.
"She has no idea the extent to which Nick is trying to take control of her career and finances. He is treating Sofia more like a bank cash machine than a bride-to-be. And Sofia is such a loving, trusting woman that she would never suspect that Nick is using her for her fortune," the source added.