I found this on the web and it works without the www but with the www it goes into a redirect loop.
Code:
# .htaccess main domain to subfolder redirect
RewriteEngine on
# Change yourdomain.com to be your main domain.
RewriteCond %{HTTP_HOST} ^(www.)?clubkourtney.com$ [NC]
# Change 'subfolder' to be the folder you will use for your main domain.
RewriteCond %{REQUEST_URI} !^/blog/
# Don't change these lines.
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
# Change 'subfolder' to be the folder you will use for your main domain.
RewriteRule ^(.*)$ /blog/$1 [L]
# Change yourdomain.com to be your main domain again.
# Change 'subfolder' to be the folder you will use for your main domain
# followed by / then the main file for your site, index.php, index.html, etc.
RewriteCond %{HTTP_HOST} ^(www.)?clubkourtney.com$ [NC]
RewriteRule ^(/)?$ blog/index.php [L]