Mombojom
She ran a 52.75 at the age of 18. The world record is 52.34 . That’s a 0.41 difference. In an event like the 400 m hurdles there are so many different little things that you can improve on to lower your time and her body will not mature and peak until she’s 22. It’s not like a short sprint where you lose legs speed after a certain age and you can only improve things at the margins..
If you follow her on social media you know that she has huge family support and she has a very outgoing personality, much more so than Allyson Felix. So if she stays consistent with her training she should break the world record by the time Tokyo 2020 rolls around, assuming she stays injury free.