The plural possessive is "ladies'." "Lady" is singular, so if you were referring solely to one woman's shoes, it would be "the lady's shoes." As for your second question, I'm assuming you're referring to a group of women in your salutation of them, so it would be "Good morning, ladies." And as you're addressing them directly, the comma preceding "ladies" is necessary.
Ladies is the plural form of lady, so the apostrophe goes to the right - ladies'. If you are wondering why we don't write ladies's, it is because ladies is one of the exceptions, along with girls', parents', players', weeks' and even Klingons' It can get a bit niggly with names too. Aristophanes' plays, but Jesus's miracles and (usually) James ...
The "fat lady" is the valkyrie Brünnhilde, who is traditionally presented as a very buxom lady with horned helmet, spear and round shield (although Amalie Materna played Brünnhilde during Wagner's lifetime (1876) with a winged helmet).
Mashable: Woman's $15 'costume jewelry' ring turns out to be worth $450,000
One lucky woman who paid $15 for a large "costume jewelry" ring got the surprise of her life after learning the ring is worth way, way, WAY more than that. Thirty years ago, an unnamed owner bought an ...
I tried searching Google Ngram Viewer for "Look lady" and "Listen lady", both capitalized so as to occur at the start of a sentence, with the hope that these ngrams would reflect the usage of "lady" in a derogatory/dismissive sense. It seems to have come into usage around 1950, and really took off in the late 1990s.
etymology - "Look, lady", "Listen, lady" – lady as a pejorative ...
I have been wondering about this little problem for a while now. Everyone understands that, in the binary, the opposite of 'man' is 'woman', and the opposite of 'gentleman' is, namely, 'gentlewoman'.