Regarding the cribbing, the seller should have told you beforehand. (And if you had a PPE the vet should have been able to tell from the front teeth, as well) Odds are, however, that her cribbing will calm down a bit once the stress of moving to a new place is gone.
My horse cribbed constantly when I brought him home, but after a few weeks it lessened and now he cribs mostly around feeding time.
You might talk to the vet about checking for ulcers, which are VERY common in OTTB's.
If you do decide to get a collar, I'd recommend the Dare Cribbing Collar
. I've tried this one as well as the Miracle Collar. They both worked to stop my horse from cribbing, but the Miracle Collar left terrible rubs, even with the fleece covers. Eventually the Dare collar left rubs, too, but not quite as bad. I no longer use any collar for my horse as he's not cribbing enough to do too much damage to his teeth.