conflict created

Calling hook OnNpcTarget resulted in a conflict between the following plugins: SleeperAnimalProtection - True (Boolean), TruePVE (False (Boolean))

This is just a warning. TruePVE  should return true 
The plugin recommendation is to return 'true' when it need to stop an action, but returning anything but 'null' works.
Also, not sure you need this plugin when you activate the sleeper protection in TruePVE.

animals can still kill sleepers only players cant using true pve I believe

Yes, this plugin prevent damage to sleepers for animals.
you can also disable the TruePVE function by removing the flag AnimalsIgnoreSleepers in the config.

but it is just a warning, a number of plugin use the OnNpcTarget  hook and return  true or null
you could also filter it out with the plugin  console-filter and add string
"Calling hook OnNpcTarget resulted in a conflict"
to the config file

Merged post

Note: I created a thread about that issue in the TruePVE section.

Merged post

Added a config parameter to disable the OnNpcTarget  hook in case you prefer to use TruePVE animal protection.
also added "OnNpcTarget return code"  config, were you can change the return code to "false" to avoid the warning message when both TruePVE and this plugin use the hook.