Tom was more solid, sooner, than Harry knew.
Ginny doesn't tell people what really happened in the Chamber, before Harry saved her.
Bill knows: he's her brother, but at the same time he's distant enough to be safe, in a way that even Charlie can never be.
She thinks perhaps she should feel more betrayed, but in all honesty, she barely remembers it. Those wounds were healed along with the others, and she thinks that to be harmed emotionally, she would have had to be conscious.
She is glad of one thing: she was too young to have a child.