Multisite with Subdomains – Permalinks without subdomain?

Hi all,

I have a multisite wordpress installation based with subdomains. My personal domain is the one with the installation. My wife has a domain mapped to one subdomain. Everything works fine. However, there is one detail we don’t like. The permalinks to the blog post only work with http://subdomain.main-domain. Obviously my wife doesn’t like that if you find a blogpost that Google is showing my domain. Is there any way to change this?

Thanks for your help!