Chances are good that the wall that the tile is on is damaged - but it's hard to say how much.
If possible, you should cut an access hole in the bedroom wall (where the mold is.) If you do this, you'll be able to see behind where the tile is & determine how bad it is, how much (if any) needs to be torn out. It may be repairable from behind. If you let it dry out, it may be saved.. You may only need to regrout or replace a few tiles. (Or you may have a huge job to do - hard to say.)
Anyway, it would be much easier to repair the plaster wall in the bedroom than it would be to retile the shower.