You're thinking too much.
1) The gal is introduced to you. But who gave you her number?
Or friend or the gal herself?
Hint: It's her advantage if she wants to reply or not.
2) Start playing hard to get?
Hint: You haven't even suggest chasing her, how could she be
playing with you?
3) What to do?
Hint: She's rude/she's not interested/she's telling you - i've got
better things to do then to play hard to get.
Solution: Move on and don't do a thing.
4) Even if you were to chase.
Hint: Should you blame anyone if she doesn't recipocate?
Solution: Be smart. Message her two days later. If she doesn't
reply, move on.
You might bump into her again.
And, don't post silly question accusing people playing hard to get.
Obviously inexperience...
Cheers