Twitter User Information

The twitter.user namespace exists for Tweets but not for Retweets so this filter ignores Lady Gaga's Retweets:

twitter.user.screen_name == "ladygaga"

To find Retweets only, use this code:

twitter.retweet.user.screen_name == "ladygaga"

To find Lady Gaga's Tweets and Retweets:

interaction.author.username == "ladygaga"