What are the signs a girl is interested?

[Svellte]

Basically the biggest sign is her behavior difference. How does she act when she is around you. Is her behavior different from how she is around other people.
A girl used to treat me coldly but when she was around other people it was normal. That's the time I knew she was secretly attracted to me but she didn't wanna show it.
Now we are in a relationship because I understood her mixed signals.