However, I suspect the primary reason for her retirement was the court ordered redrawing of her district lines. The district used to extend down to the southeastern coast of Miami-Dade county from Hialeah, and Little Havana to Homestead. It also included the exclusive Key Biscayne neighborhood off the port of Miami. With the new lines, the district loses Homestead and it's mostly Republican constituency and pick up some surrounding Democrat neighborhoods in Miami.
In 2016 they re-elected Ros-Lehtinen by 9 points but the district went for Hillary Clinton by 10 points.
Cook now Rates the District as D+5 and it should be an easy pickup for the Democrats in 2018.
If not, then the Democrats will been in real trouble.