Hello and welcome to AA!
I'm sorry about your troubles with the betta. In my experience once they act they this, there isn't going to be much you can do about it. She's most likely just not a candidate for community living. You could try to re-arrange the tank and maybe add some new plants or decor. This might buy you some time, but my guess is the behavior will start up again. Most female bettas will never bother another fish..especially one like a cory...she's an aggresive one and I'd say this just isn't going to work.
I also want to point out that IMO
panda cories belong in tanks of 20 gals or more and because they are a shoaling fish they should be kept in groups of 6, definitely no less than 4.