Lauren Conrad On Her Breakup With Jason Wahler

"Breaking up with Jason was the hardest thing I've ever done," the Hills star, who recently celebrated her 21st birthday, tells CosmoGIRL! in its March issue. "I still wanted to be with him but I knew that I couldn't be."

She helped mend her broken heart with the aid of a pal: The Hills costar Heidi Montag. "I was so fortunate to have Heidi, who is my best friend. She took me away on a road trip to Las Vegas, and we had the best time," Conrad says.

"It was important for me to know that I could still have a good time without a boyfriend. I slept in her bed for a month because I couldn't go into my room. The only thing that heals a broken heart is time. But it really helps hanging out with your girlfriends as much as possible."

Now, Conrad, who was recently named the spokesperson for Avon's mark. brand, is focused on her career: "I've been given an opportunity with Laguna Beach and The Hills, and my father – who is the smartest man I know – has advised me to capitalize on those opportunities," she says. "So that's what I'm trying to do – make contacts, get to know people. Hopefully that will help me as I start moving into my fashion career."