Heidi Klum has promised Mel B she'll ''always be there'' for her after she recently checked into rehab.

The Spice Girls singer works alongside the 45-year-old model on 'America's Got Talent' and she is so proud of her for seeking professional help and has reassured her that she'll always have her back.

Speaking to 'Entertainment Tonight', Heidi said: ''I'm her friend and I've been her friend for a really long time and I'm always going to be there for her and help her with whatever she needs help in.''

Mel's boss Simon Cowell has admitted he has ''a lot of respect'' for the 43-year-old singer because she leaves her personal issues at the door when she arrives on set for the show.

He explained: ''Mel's a trooper... she comes to the show, leaves everything behind, focuses on the contestant. That is a true professional.

''She's so professional, it's all about the contestants with her, so a lot of respect for her.''

Her other co-judge Howie Mandel is also amazed by the brunette beauty's professionalism at work.

He added: ''She's a very strong, wonderful lady whose battled what a lot of people battle. I'm just amazed at how she can show up and be a true professional and just a wonderful person who is entertaining and I'm thrilled and I feel lucky that I get to sit beside her and that America gets to enjoy her and watch her and listen to her. I hope that she would reach out and I'll reach out to her. She's a friend and I think we have to be there for our friends and people we admire. And she's certainly someone I admire and whatever she wants from me and needs from me, I'm there for her.''

Mel recently revealed that she turned to rehab after she was diagnosed with Post-Traumatic Stress Disorder following her father's cancer diagnosis nine years ago and leant on therapy more when her ''intense'' relationship with her now-ex-husband Stephen Belafonte broke down last year.

She said: ''Well, it kind of got a little bit skewed with. Let's put it that way. Now, I've been in therapy since my father got diagnosed with cancer nine years ago ... My therapy changed a little bit because I was in a very intense relationship, which you can all read about in my book, which is out online now. Alright. So, I do address a lot of those issues. But you know, no, I'm not an alcoholic. No, I'm not a sex addict. You know, I was with the same person for 10 years and that was quite a turmoil, very intense. That's all I can say about it. I'd like to say a lot more, but let's just keep it PC. But ya, I address a lot of those issues and I did kind of have to ease my pain. I do suffer a lot from PTSD.''