Now, nine weeks after her dramatic transformation, Montag is dealing with the horrified reaction of her mom, Darlene Egelhoff.
"I still can't believe I'm 23 and mom is reacting this way," Montag tells PEOPLE. "I'm nervous to go home and face her – especially with cameras rolling."
A source close to the family tells PEOPLE that Egelhoff "is horrified and having a total breakdown. She can't wait to confront Heidi when she goes home."
Montag's mom, who lives in Colorado where the reality star grew up, will get her wish soon. "Heidi is planning to head back to her small town of Crested Butte very soon," says the source.
And Hills fans will get to see the drama play out next season on the MTV hit, as cameras will catch every moment.