Luna was just happy that they could still talk normally. She didn't know what she would have done if Mark refused to talk to her after her confession. She knew that she would deserve it, but she wouldn't be happy about it at all. Even before she fell in love with him, Luna felt that Mark was a good friend, someone she could talk to, and that was very important to her. Losing Mark's friendship would have really hurt.
Your gift is the motivation for my creation. Give me more motivation!