shes clearly not comfortable enough to meet up with you alone yet, else she would have met you!
I had this for the past 2 months with a girl...she wanted attention but was clearly too chicken shit to meet up...so i arranged to meet her out with her friends as i knew she would be more comfortable this way and at least get a shot at seeing her and creting the attraction...so met up with her,k-closed a few times and the game is now on. next time will probably meet up alone..but hey if she flakes again and oesnt want to meet up and is still a bit shy, then i'll meet her out with her friends again (and bring mine along too of course, very important to not rock up alone!).
Some girls just dont like the confrontation and need more time to get comfortable with you. so...ask her where shes going to be one night, and tell her by coincidence your friend has been asking you to go there too! fancy that...but say youre probably not going to go! then you will see if she realy wants to see you or not. (make sure you take friends along, at least one wing... else you'll look like a desperate tosser)
and sorry to answer your main question which was 'should i freeze her out?' with not replying to her...rather call her out on her flaking...just write back saying 'oooh heeere we go again, another flake from the flaker herself!
'. this time she will feel like a loser if she DOES flake as she knows its not working on you and that you know what shes trying to do.