If the penalty is greater if the victim commits suicide some victims will choose suicide in order to punish the bully more. The actions taken while bullying and the severity of those actions should be what counts. The victim's subjective distress should matter in so far as the bully could have reasonably been expected to notice the victim's distress would be greater than your average victim under the same circumstances. It is people's intentions as well as people's recklessness that determines culpability, and those variables are the same regardless of what the victim does in response to the acts.
Punishing bullies more because the victim commits suicide will lead to more suicides from victims who want revenge. Instead whenever bullying is severe enough to be punished it should receive the same punishment whether the victim is resilient and relatively unaffected, whether the victim becomes depressed, or whether the victim commits suicide.