Carrie had a very marketable backstory. From garlic bread factory to single Mum making a success of herself. It's a great arc but I think she feels lost now she is actually by all accounts pretty middle class in regards to the life she seems to lead.
I think to try and keep 'relatable' she really always pushes so hard against anything that seems middle class because of her own feelings of not really fitting anywhere. She seems very much someone who wants to seem aloof and cool due to insecurity and or fear of rejection. The type of bully girl at school who would lash out first. I feel like almost anyone who gets cosmetic help has some inherent feeling of not being 'good enough' so it fits. She is a beautiful woman and was before fillers etc.
Same with her push against commitment (whilst married
). Basicly a walking childhood trauma open wound who could benefit from a dash of therapy.
ETA. My bet on the shocking backstory to the marriage is that Sam is Christian so no sex before marriage. Got married to shag?