Sad, but she was correctly treated by the Law in 1955. There could have been no other verdict. She admitted murder in open court, such that her own barrister realised he could not address the Jury on her behalf... The Court of Appeal vehemently dismissed her posthumous "appeal" in 2003.
Whether or not she should have been hanged is another matter. The tragic aftermath for her son especially, and possibly her sister and ex-husband, was something I'm sure the Law did not contemplate...
The problem with the death penalty in the UK was that the final say rested with a politician - the Home Secretary. Only about 50% of men sentenced got to meet Pierrepoint, and only about 13% of women.
Ruth Ellis's timing was poor, coming just after an election in which the Tories had won specifically on a platform of "law'n'order", and she was also unfortunate to have slightly injured a passer-by with a stray bullet - supposedly the clincher in Home Secretary Gwilym Lloyd George's refusal to commute Ruth's sentence. The government could also not be seen to bow to public petitions...
As Pierrepoint himself admitted - when he turned against the Death Penalty:-
"Of course, NOBODY wanted it for EVERYONE, but NOBODY could agree on WHO should GET OFF..."
I urge everyone to watch the amazing
"Lady Killers" episode from 1980, starring the late, great
Georgina Hale (who died earlier this year, aged 80)
https://www.youtube.com/watch?v=Zh46SukWHSs