She was kind to a stranger, who asked her for a drink.  The stranger can see the well and probably   fetch water for himself. But Rebecca did not point this out to the stranger rather  she indulges him and gives him some water to drink.

She noticed if these people were thirst then their camels must be thirst too. She proceeded to offer water to their animals. According to the national geographic, a thirsty camel can drink as many as 30 gallons (135 liters) of water in about 13 minutes.  This generous act would have taken considerable effort and time as she gave water to  10 camels.

For her kindnesses, readiness to serve others and hospitality she received unexpected gifts