One prominent point of comparison between the two girls is that their inner traits are so different. Angela is vindictive, manipulative (which is an intentional action, not an inadvertent behavior), vengeful, vain, and self-gratifying. Cathy is compassionate, accepting, giving, concerned for others, and generous with her affections. The girls are opposites of each other.
Obviously. Cathy is shown to have a loving family environment that supports her and cares for her. Note the way in which the family works together to support M&M and take care of him when he is found. This, in a large way can be said to be hugely influential in the way that Cathy is a very mature and stable character. If we compare her to Angela on the other hand, Angela is clearly a chaotic character whose lack of a secure and stable family base can likewise be said to have been hugely influential in the way that she has turned out.