The 23-year-old 'Love Story' hitmaker asked the pop diva to make a cameo at her concert in Los Angeles, but Lopez was apparently unpleasant to deal with, reported Showbizspy.
"Jennifer was extremely rude to some of Taylor's closest friends backstage. Jennifer made it clear they shouldn't look in her direction or speak to her," a source said.
"Now Jen is on Taylor's bad list - right along with her numerous exes. Taylor has decided she will never work with JLo again or even invite her to a performance," the source added.