The most detailed version of her story came via Crump at his March 20th press conference. Here is the CNN transcript with Crump's statements towards the end:
http://transcripts.cnn.com/TRANSCRIPTS/1203/20/cnr.03.html
I think problems with the girlfriends account are going to be much worse then just witness tampering. According to Crump's press conference she NEVER came forward to anyone on her own. Crump says TM's father figured out on March 18th that TM's girlfriend had been talking to TM almost the whole afternoon of 2/26 up to 7:16. Her story related to the media on March 20th is that GZ clearly had stalked then chased TM who was trying to get away but was eventually cornered and then pushed when the call ended.
Now that is when I think most people would have thought to call the police. Like right after someone you were talking to on the phone was stalked and then attacked, right? But she didn't do that.
OK, maybe she was worried about TM but didn't think calling the police would be helpful since she may not have known where TM was and she just hoped for the best. That seems weird to me but I'd be willing to give the teenage girl a little leeway here but why didn't she contact the police as soon as he found out TM had been killed? She's literally the prosecutions best witness for a large part of the timeline and she didn't think to tell anyone even after she found out TM had been killed by the very guy she knew he had tried to run from when TM was talking to her.:banghead:
Even after three and half weeks of a media firestorm with masses of people rallying around the cause "Justice for Trayvon Martin" she never apparently thought to herself, "gee, I might be able to help with that." TM's family is lamenting the failure of the SPD to properly investigate the case but according to the Crump the best witness who "connects the dots" never connected the dots for anyone before March 18th when TM's father contacted her.:banghead: