We can hypothesise as much as we want to why girls do things.... We'll never figure them out loll
But imo girls will always be hesitant in this day and age.
Especially with so many troubled individuals and especially since she doesnt know you.
I think the time when a random guy asks a girl out who she doesnt know is over
With social media so prominent why wouldnt a girl do her homework on you first to see if youre even worth it?
I say exchange contact details and/or add friend on social media and take it from there!

Goodluck!