She may be unreliable as far as her commitments to her agency goes-this is not all that unusual.  That would not be something that shows up in her reviews since once she is actually at her in call and on the schedule she is not likely to miss any appointments.

I had an agency fav several years ago who was constantly mising flights and arriving late or leaving early if she wasn't busy enough.  None of this ever showed up in her glowing reviews since her customers were, for the most part, none the wiser.

I think it's bad form for the agency to slam one of their own providers. Providing a list of alternatives is not a bad idea but I wouldn't be making suggestions until the first gal was actually flaking...

Just as an update to this thread, I responded to the agency adamant that while I appreciated the list of other ladies the one I asked after was the only one I was interested in seeing.
Interestingly enough after a couple of emails back and forth whats come apparent is the difference between the two people at the agency end who have been responding.
The one who has been professional and polite and the second who has basically downplayed and trashed the lady in question.