There is an extensive thread in the community about requirements to be a flight attendant..
From a post within that thread the answer to your question is "There is not a height or reach requirement to become a Flight Attendant for Southwest Airlines. "
and here's the thread:
https://community.southwest.com/t5/Southwest-Careers/Hiring-for-flight-attendants/td-p/55713/page/1
Good luck in your quest. It may take you a while due to the fact the no airline is hiring at the moment -- due to the impact Covid is having on air travel.
