Marlene is a social opportunist in that she does not have flesh and blood friends, she prefers to surround herself with long-dead or fictional characters to associate with. Marlene puts herself with this group of women who all achieved some measure of success, but at a great price. Marlene feels that these women are the only suitable social companions for a woman of her stature.
Marlene is a personal opportunist because she was able to give up her child, on the basis that she did not wish to be encumbered with a child. She gave her child to her sister, in part because her sister seemed unable to have children, but also because it was the easiest way to rid herself of a nuisance.
Marlene assesses what opportunities will best benefit her, and gives no thought to the ramifications for anyone else. The irony being that Marlene has been left with an empty life because of those choices.