"Get a Life!" she said, and left. What she did not realise was that, from his perspective, she did not have one at all.
"A Life" is something everyone has had, or will have had by the time they die. How they choose to fill it is a series of personal choices and coincidences that lead to a patchwork made up of labour, leisure, relationships and knowledge (to name a few components of this weave). The quilt matches others- or it does not. What is generally implied by this suggestion is: "Why is your life not like mine- something I can understand."
Some will follow up on this suggestion. Others will not. Either way, this does not change the fact that they have a life. How they share this is up to them.