Answer and Explanation:
The expression "keeping up with the Joneses" is used to refer to people who keep comparing their lives to someone else's, usually in a way that makes them feel bad about themselves. If you are keeping up with the Joneses, you are constantly dissatisfied with what you have, feeling envious of what others possess or of the lifestyle they display.
That is what the psychologist quoted in the article means when she says "Social media can be the modern day version of 'Keeping up with the Joneses.'" Social media has made it possible for us to compare ourselves to all types of people all the time. We do not depend on TV shows to see the lifestyle of the rich and famous anymore. Anyone can display their lives, relationships, possessions, or bodies online. And, since people tend to show only the happy, luxurious, "perfect" side of their lives, we tend to think of our own lives as lacking, as inferior.