Kim played the role from 2002-2005, then when John Yorke had a big role at the BBC in the late '00s, he brought Danniella back and tried to make the character very tarty and ridiculous (which she had never really been to that degree before). Danniella was there for part of 2009, for a few parts of 2010, then returned briefly in 2016 for Peggy's funeral. Danniella's behavior was erratic enough in the '10s that I was surprised she was asked back in 2016. I wonder if that led her to think she would always get to come back if she wanted to do so.
Most of Sam's time with her family was with Danniella - Kim was only on the show with Barbara Windsor for about half her run, and Steve McFadden was also gone for the last year and a half of her tenure. I sometimes wonder if that is why Danniella returned for those last few stints.
I do feel bad for her, but she has been deeply unstable for a long, long time.