"It's really important to emphasise that, of course we're professional athletes and we have to be fit to do our sport, but a body shape doesn't determine if you're fit enough," Euro 2022 winner Kirby told the BBC.
"A lot of people see athletes as robots."
One in five players were the target of online abuse during the 2023 Women's World Cup, FIFA said last month as a package of social media protection tools hid nearly 117,000 comments.
More than 150 players received targeted discriminatory, abusive or threatening messages during the tournament in Australia and New Zealand.
A knee injury kept the 30-year-old Kirby out of the World Cup, part of a string of physical issues throughout her career including a heart condition with which she was diagnosed in 2020, and the layoffs have led to negative comments about her weight.
"Coming back from an injury, you're not going to be in the best shape of your life," she said. "It was quite hard for me a few years ago after my heart condition. I'd been out for a while and had gained a bit of weight because I physically couldn't do anything.
"It's not like we train for a week and suddenly you're fully fit and ready to go. It was tough reading those comments."
Missing the World Cup was heartbreaking, but Kirby said she was proud of her England team-mates who lost to Spain in the final.
"Of course, missing a World Cup is not a nice feeling at all, there was always that feeling inside, wishing you were there," she said. "But I made a decision very early on (after knee surgery) that I wasn't going to let it affect me. I didn't feel that would do me any good."
Since returning from her knee injury, Kirby has made eight appearances in the Women's Super League for Chelsea, who top the standings three points ahead of Manchester City.
Kirby has scored 103 goals in all competitions for Chelsea since signing in 2015. She has six months left on her contract and said there have been no conversations with the club but feels that she can still be a key player.
"I want to continue playing football and continue playing football at a high level," she said. "I still feel I have a lot to give wherever I am, whether that's at Chelsea or that has to be somewhere else. But I love the club."
