This is less about Denise Welch herslef than the media perception that has been created around her.
It happens to a lot of people in the public eye - the media decide they have a certain 'personna', and will profile them accordingly.
Gary Numan told me that he was always portrayed as 'miserable' by photographers, who woult take dozens of shots of him smiling, then catch him gazing into space unsmiling, on an 'off-camera' moment - and that would be the shot that was used. I know from knowing him that he is a warm and witty man - just very shy.
I am sure DW is similarly perfectly well behaved except on occasions where she gets a bit tired and emotional - and the press are there to increase the public perception that she is a 'loose woman' in more ways than one.
It's the price people pay to be in the pblic eye - they have no choice.