Robin and Tracy's relationship is actually somewhat complicated. They start out friendly towards each other when they meet in The End of the Aisle. In Last Forever - Part Two, they are still friends, but their relationship starts to strain on Robin's end after Barney and Robin get divorced in 2016, and Robin soon realizes she still has feelings for Ted (of which, Tracy seems unaware). Robin's feelings might have been what prompted her to move to Morocco and Greece. Despite Robin's feelings for Ted, she does attend Tracy's wedding in 2020, at Tracy's insistance.