Don't city/regular colleges check and validate high school diploma of admission applicants?

One of my San Marino High classmate Samantha was bragging about her cousin Chi-Han Hung or Huang dropped out middle school and did not go to high school. Few years ago, my classmate's father ask his friend in China to provide her a fake high school diploma so she went to PCC for few years. Now, she gets admission to transfer to UCLA and UC Berkeley. Is it possible? Don't colleges check and validate all school record any more?