mod rewrite confusion

[Bob_123]

I'm confused and would greatly appreciate some guidance.

I have the following directory structure and wb sites respectively:
site_1_dir: "public_html/WMF " (my primary domain subdirectory)
site_1: "www.wmf/WMF/"
site_2_dir: "public_html/mmf" (a subdomain)
site_2: "www.mmf.com"

I want site_2 to redirect to site_1 transparently. (That is, when the address of site 2 is used I want to execute the code in site 2. I want this to be transparent such that the site 2's address is displayed.)

Here's my last attempt....

RewriteEngine on
RewriteCond %{HTTP_HOST}!^www\.wmf\.com$
RewriteRule ^(.*)$ /www\.wmf\.com\/WMF/$1 [L]

Thank you in advance,
Bob