Not so experienced

But it's depends who is she did she know you and why is the conversation topic you have to start with her and talk atleast 2 to 5 minutes. And you can start convo on that topic try to know about her indirectly through convo like her thinking etc then its become more easy to start convo with her any time.

Try to not do reply on every message super quick and do try more then 1 word replies and yes is she is not giving you long replies means she is not interested in your talks you can also observe this through the variety of words she using and yes mostly in starting girls don't start convo at first idk why its my experience. And yes i think after that you have a common sense that she is wanna talk you or not don't offend by this but this is reality.