Speaking at the European Premiere of "Killers" in London last night, Katherine explained to reporters that she finds it tough leaving her daughter Naleigh behind, "It's difficult but it's like any working mom I think you have to make some compromises. It's easier said than done, but I knew that I wanted to keep working, I love what I do but it's really hard to leave her - I feel horrible."

Katherine revealed, "It's weird. We've been iChatting a little bit and I never used to do that much because I felt a little self-conscious because when you iChat you're literally staring at each other and when you have a real conversation you look around. I don't normally do it but because of Naleigh I'm like this is a great tool to have. She just has been reaching for me. She sees me but she understands that she can't touch me and then I feel horrible - I feel like a terrible mother. So yeah it's weird, it's hard."

Katherine Heigl Signing Autographs At The European Premiere Of Killers In London Katherine Heigl Signing Autographs At The European Premiere Of Killers In London

In an interview with Metro, Katherine also explained how she was inspired to adopt Naleigh by her own mother Nancy.

"It's so funny. My mum and I joke about it when people say 'you're just doing it because it's trendy'. My mum says 'Well, I'm trendier than everybody because I was doing it in the 1970s when I adopted your sister."

"I'm very grateful for this little being in my life. I'm very grateful she's my daughter. I'm so grateful we found each other. It's not so much about her being adopted. I just wanted to be a mum and she needed one so here we are."

Katherine added that she was missing her husband Josh Kelley, who is back at home in Los Angeles with their daughter, "I'm still so infatuated with him. We've been together four and a half years so you'd think by now it would start to feel a little bit calm but I still think he's so hot and so sexy and he's a great dad."

One other thing Katherine missed was being Punk'd by "Killers" co-star Ashton Kutcher during the filming of the movie. "Everyone keeps asking me if he Punk'd me and he wasn't like that at all - he was pretty serious and he's a really professional businessman. He's got a lot going on in his company and stuff so he wasn't that jokestery prankstery guy. And then I started thinking 'well maybe he didn't like me. He would have Punk'd me if he loved me!'. So now I'm offended he didn't Punk me," she said laughing.