I'm writing a drama and need some help. Can a criminal lawyer in a rape case switch sides from the person they are representing to the victim if they have been fired by their client?
No. As the defendant's lawyer, they will have been privy to privileged communications. As such, it would be unfair to the defendant if they now started prosecuting.
Also note that a victim very rarely has their own lawyer in a criminal case. The prosecution lawyer is acting for "the Crown" (essentially, "society as a whole"). (There are exceptions, if the victim is bringing a private prosecution - but this is very rare for serious cases such as rape).