Merge Replicate and Mirrors
The only answer here, unfortunately is that mirroring is only supported for the pulbisher and only if the distributor is on a different server from with the principal or mirror. I would recommend a dedicated server for the distributor, but even using the subscriber server would work.

Database mirroring is not supported for distributors or for subscribers, and the work-around for mirroring a subscriber as detailed in the whitepaper by SQLCat only works for transactional replication. You could still use the manual sync option if you want to try to do something similar, but you'd have to get the data in perfect sync yourself which is very difficult to do unless you stop traffic to the publisher.