Kate Walsh managed to turn her witch-of-a-character Addison Montgomery into one of the most beloved characters on Grey’s Anatomy, and now she is headlining the most anticipated show of the year – Private Practice. As the cover girl lounges on the beach for her Entertainment Weekly cover shoot for the annual Fall TV Preview, she talks about her goals, leaving her friends behind, and her excitement about her new adventure.

When Grey’s Anatomy creator Shonda Rhimes cast the actress in the first season of Grey’s, the plan was to have her around for a handful of episodes, as the no-good tramp who cheated on McDreamy (Patrick Dempsey), so it’s impossible for Walsh to have known she’d end up with her own spin-off. “I definitely like writing down goals, where I want to be, how I imagine it. But I didn’t write this down,” she says. “I didn’t write down I’d like my own spin-off.”

She had actually planned for a hasty departure. “After the initial five episodes, I shot another pilot for ABC,” says Walsh. “There were always a lot of half-hour shows to do, so I thought, That’s probably going to be my life.”

Once Rhimes came up with the spin-off concept, ABC execs – to cover their bases – inserted a spin-off clause into cast members’ contracts. Though initially surprised, Walsh said she didn’t read too much into the clause because none of the cast knew about Rhimes’ plans. “We were like, What’s this? We had never seen it before,” she says. “We just thought it was a part of negotiating.” That is, until Rhimes beckoned Walsh into her office in February. “It was like I was being called to the principal’s office,” Walsh recalls. “She told me she wanted to spin off my character, and then I slowly started to leave my body. I was very excited about it, obviously, totally thrilled! But my first thought was ‘Oh, God, what if it doesn’t work?’”

What does Rhimes have planned for Addison’s character? “I don’t think anybody wants to see Addison jump into a relationship,” says Rhimes. “I don’t think she’s ready for that.” It’s hard to be ready when she still has emotional ties to Seattle Grace, which is why she will return to her old workplace one last time on the Grey’s Sept. 27 premiere. This is where it gets a little sad for Walsh. “I’m friends with all of them [at Grey’s], but even as my character, I’m thinking, ‘Wait, can’t I just take a friend with me to California?’”

“There’s definitely real melancholy, and a loss,” continues Walsh, of her big move. “But I also feel like it was right, just like when it’s time to go off to college. This is the right time for me to go.”

For more on this fall’s TV lineup, check out Entertainment Weekly‘s Fall TV Preview issue on newsstand’s Monday, September 10th!