is is possible to check whether a virtual function is override from parent class

[Chatouille]

Decorate OnTriggered with UFUNCTION, then you can do this :

if (GetClass()->FindFunctionByName("OnTriggered") != ThisClass::StaticClass()->FindFunctionByName("OnTriggered"))
{
    // is overriden
}

This should work for blueprint overrides also (for BlueprintNativeEvent).