User 1 sends the event to User 2 via P2P instead of pushing through a relay. Then User 2 can send to any relay it wants for backup and to share with other clients the same user uses.

Amethyst would just send it to your own write relays for backup for now. And we could have an option to turn that off for the privacy-conscious users. In that case, no event received via P2P ever leaves the phone.