It would probably make more sense to use one of the filters described in:
As modifying the plugin will result in losing your changes if it’s ever updated. Something like this would display the screen name with link before each tweet:
add_filter('latest_tweets_render_tweet', function( $html, $date, $link, array $tweet ){
$screenName = $tweet['user']['screen_name'];
$twitterUrl = 'https://twitter.com/'.$screenName;
return '<a href="'.$twitterUrl.'">@'.$screenName.'</a><p class="my-tweet">'.$html.'</p><p class="my-date"><ahref="'.$link.'">'.$date.'</a></p>';
}, 10, 4 );