Step-by-step explanation:
For Georgiana: It was about the flaws each and every individual has. No one is perfect, even though some may say the "yes, I'm perfect and so are you!" so and so. No! For Georgiana, it was a symbol of being human, for being who she was, and not for anyone else. The birthmark meant that she was special and unique in her own way.
For Aylmer: It simply meant about perfection and greed. He was blinded by perfection and the comments of others that made him so obsessed with the word 'perfect' and 'beautiful', that he went to extreme lengths to make that happen, not knowing it would affect him and Georgiana greatly later on. He was blinded by greed. He had Georgiana, no one else did. So, why not make it more? Why not create and transform her into someone who she wasn't. Without the birthmark, Georgiana was simply not Georgiana. She was another person, someone whole new different that Alymer created.
hope this helped!