Late last year she agreed an out-of-court settlement with the government before her case was due to be considered at an employment tribunal.
She has now spoken out publicly for the first time during a guarded interview, although she declined to go into details of the meeting with Mr Cummings.
She told BBC Woman’s Hour: “My first emotion was just what can I do to stop this happening again and it wasn’t until I’d say maybe the very end of last year that I’d really processed it as we came to the end of the legal case.
“I think there is a sadness that hits you because you feel you worked so hard to get a seat at that table.
“I spent five years in five different government departments and I started as a door knocker, someone who put leaflets though people’s doors…I’d really worked from the ground up.”
She added: “I think the sadness is around the fact that were there enough people from other backgrounds sort of like me to be the voice for other people?
“And so the reason I wanted to come on and speak to you was to try and encourage those other people to come forward.”
No reason was given for Ms Khan’s dismissal, but it is thought she was accused by Mr Cummings of leaking Brexit details.
Ms Khan strongly rejected the claims and repeated that again today, describing the accusations as not right or fair.
She added: “I was never given a reason about why what happened – happened – and that for me was the sort of trigger to take the action that I did, which is the legal action that I’m referring to.
“Nobody ever said it was because you did X, Y and Z. I know there were lots of reports in the media but none of that was ever put to me.
“I remember at that time feeling quite strongly that if I’m not given a reason and if there’s a chance that this could happen again, it sets a really bad standard and a precedent.
“Especially for a lot of the advisers who were coming into that Government who were really young at the time…so I felt like I had a real responsibility to them.”
A Government statement read out on Radio 4 said: “Special advisers are temporary civil servants. It’s an important point of principle that ministers can select their special advisers and therefore if they lose confidence in them can dismiss them and this remains the case.”