"Hi, Lilly." 'Yana definitely be close enough. After all, she was used to the other New Mutants calling her that, and Kitty as well.
She stayed in place and let Lilly decide how much to approach her. She had to consider how she should treat the child. In a conversation with Loki, she had mentioned lies serving a purpose. It might turn out best not to be honest with this child about whatever the situation was.