How to Overcome Jealousy in the Workplace

The 23-year-old says she has a wall up when it comes to doing things outside of work talking about personal lives building friendships. She used to be in a team with a girl a year younger than her and we became absolute best friends. The friendship quickly turned sour after about eight months due to her spreading rumors behind my back lying to hire management, painting me out as a bad person. Her dilemma now is: How can I get over this? Is it wise to get friendly with people from work to take it outside of work? Like, is that a smart thing to do? How much do I share with someone at work?