Unless EC2 is much different than other servers, you should be able to install another WordPress installation under another directory.
For instance, you could have
/var/www/html/blog/ with WordPress installed and
/var/www/html/blog/wordpress with another WordPress install.
You can either use a separate database or use the same one as the other install, but you would need a unique table prefix set in the wp-config.php.
You can read more about multiple installs here:
I've never used EC2, but I would assume it would work very similar to any other server. If not, you may want to reach out to their support to see what the differences are.