The phrase emphasizes that actions are more credible than just words. She claimed to be environmentally conscious, and indeed, she walks the walk by using public transport.
Pro Tip 2/3
Sincerity Check
Use it to question whether someone’s actions match their statements. You said you'd help the homeless, but it's time to walk the walk.
Pro Tip 3/3
Not Literal
'Walk the walk' is metaphorical; it's not about actual walking. He talks a lot about team spirit, now he has to walk the walk during the project.