Montag was "horrified" when Chase showed up while she was filming a cameo in the upcoming comedy Just Go With It on Monday and began "demanding a significant portion of her Hills money," a source told Us.
In addition, the source claimed that Chase attempted to "move onto" The Hills co-star Audrina Patridge and attempted to offer her spiritual and managerial advice last week when the she and Montag were filming a scene for the MTV reality series.
"He's this creepy older guy who is clearly preying on these young girls. It's awful," a source told Us about the 40-year-old psychic.
"The guy thinks he's famous now -- it's ridiculous. He's referring to himself as the most famous psychic in the world."
Pratt had managed the couple since they met almost five years ago before Montag announced the decision to hire Chase.