Hardly admiringly...
Were you and your high school friends admiring young girls when you told each other which girls were easy ???
Kid 60 years ago the Aussie guys used ‘Sheila’ to mean a woman was a slut and that hasnt changed regardless of how many FaceAcheBook type lexicons you read...
I haven’t found a single dictionary definition that defines it in the way that you do. I’m sure they have slang words for ‘slut’ and someone might say, ‘That sheila is a slut’. But Sheila itself is simply the female version of ‘bloke’, and the average Australian woman wouldn’t find in it an insulting sexual connotation.