Cage match is a wrestling match, not a magic match. It involves physical combat, not magic. Terra would sooner teleport herself out of the match than hurt her friends with magic regardless. Sabin, Shadow and Umaro would have no such issues - Sabin would consider it a fun game (he would only knock them unconcious, not kill them), Shadow would have no qualms fighting anyone, and Umaro already throws his opponents around in the game so I don't think he'd have a problem throwing them into the side of a cage, either. Terra would never do anything like that, and wouldn't stand a chance in physical combat against any one of them anyway. They're simply better than she is.

If it were a magic fight, yes, Terra would win (although let's face it, if anyone who thinks that magic and all that were actually allowed would still be able to get past Celes in the earlier round has clearly forgotten something).

Cage. Match.

EDIT: Is this a first pin = win, or an elimination match, Mulley? Is this the last round?