Seek her out yourself (and you've prepared)

You always knew there was the possibility that your parents' plan would require you to abandon Rosie, no matter how temporarily, an eventuality that you wouldn't be able to accept. So you planned for it. You legally obtained a firearm that has never left your side since, you made sure to pack double safety supplies, and you planned your own routes to the compound that would allow you to pick her up quickly.

The route in question follows your current route for perhaps the first mile, so you have time before leaving. You could announce your plan, and risk your father trying to stop you, or you could slip away quietly and risk getting a stern talking-to when you arrive.