Alejar equates to many different verbs in English. For your two examples: Aléjate de ese lugar = **Stay away** from that place. Entonces ella se alejo lentamente = Then she slowly **walked away**. Here are a few others: Al acercar o alejar el mapa, la vista general también cambia = As you pan or **zoom** the map, the overview map also changes. Quiero alejarme de ti = I want to **get away** from you. Si el dispositivo no funciona, intente alejarlo de los demás dispositivos semejantes = If the device is not working, try **moving it away** from other similar devices.

Google Translate defines "alejarse" as "move away", so I guess an example would be "The police ordered the suspect to move away from the car"

alejate de ese lugar, or entonces ella se alejo lentamente

please provide a sample sentence in spanish so we know the context please:)