When Daisy and Gatsby are first courting, she says to him "Rich girls don't marry poor boys" and demonstrates that she is not strong enough to bear the disapproval that would result from marrying below her social status. This comment and Daisy's refusal to marry him despite their love affair is what galvanizes Gatsby to become a self-made millionaire. This quote shows her weakness and lack of courage, as well as her refusal to give up her social standing. She will not stand up for Gatsby or defy convention, and prefers instead to depend on others to fulfill her needs and whims.
When Tom and Daisy returned from their honeymoon several years ago, Jordan tells Nick, she had never seen a woman so "'mad about her husband.'" Jordan says that "'If he left the room for a minute she'd look around uneasily, and say: "Where's Tom gone?" and wear the most abstracted expression until she saw him coming in the door.'" Daisy seemed to dote on Tom, stroking his face with his head in her lap. However, this is a very different picture from the Daisy Jordan saw on the day of her wedding, when she got very drunk and insisted that Jordan go tell everyone she'd changed her mind. Before this, Jordan says, Daisy had been in love with a young officer, Gatsby, who left for the war, and after that, she only kept company with men "'who couldn't get into the army at all,'" presumably because they would never have to leave her. Thus, it seems like Daisy is rather bad at being alone; she needs a man in her life, and this is why she simply could not wait for Gatsby to return. Perhaps she needs a man to feel whole, to feel desired. Perhaps she is incapable of being alone because it frightens her or because she doesn't really like herself very much. But her pattern of going from one man to the next is undeniable, and therefore it does seem as though she relies on men.