How big She is ??
I have sometimes similar problem..
I prefer offer my Balls smaller meals but sometimes I dont have choice and will end up with mediums...
You can try buy weaned(just open eyes eat drink by itself) rats 30-44g...
Feed 2 smallest first week.. after that next 2-3 weeks one.
If you afraid that last one could be to big and next show is next week.... If she have nice meal week ago You can skip one week without problems... In meantime I'll try to convert her to F/T... or If you Have more snakes maybe start breed your own feeders...