In addition to protecting 2 presidents herself, Cheryl trained other agents, and she joined us Tuesday on "TMZ Live" -- in the wake of Saturday's attack -- to counter those hating on female agents, and to explain how difficult it is for any agent to get that detail ... whether they're female or male.

As Cheryl put it ... being a part of the Secret Service is no easy thing -- it's an elite group of specialists who are put through rigorous training and probation to earn the detail.

She added, "So, for those who believe women don't belong there ... that's fine. There are a lot who believe women don't belong anywhere but at home -- and that's their preference."

While Trump's Secret Service detail appeared devoid of female agents Monday night in Milwaukee at the Republican National Convention, Cheryl said that could easily be a coincidence -- due to schedules -- and not a response to critics.

Cheryl's insight comes hours after Secret Service Director Kimberly Cheatle broke her silence on Saturday's shooting, telling ABC News she takes full responsibility for the whole ordeal, which she called "unacceptable."

However, Cheryl felt differently about the agents' reaction to the attack, as she commended her peers for doing exactly what they were trained to do ... which is to become human shields for Trump.

She continued, "The president pushed up and got up. That was his choice. But the agents huddled the way they were supposed to huddle."