personally would contact beretta and also local gunsmith that you trust.
the tricky part about sending the gun back to beretta is that if they decide to replace the frame and issue a new serialized lower, it will have to go through an FFL and you may have issues finding one willing to transfer. i've heard many such stories of people sending a damaged frame back to glock (or whichever other mfr) but then they're stuck because they are unable to receive the lower via FFL.
if it's a small enough piece of the rail that broke, you might be able to re-finish any rough edges and just keep it well lube (personally i would keep grease there).
how did the thing break? depending how old it is, i would consider replacing your recoil spring as if the spring is old and shot-out there will be heavy slide -> frame contact on cycling.
maybe post some pics up here and you might get some better input. i do not own a jetfire .25 but i do own a 21A bobcat (in 22LR) so i'm vaguely familiar w these tip-up barrel designs. great little guns.