The Chelsea forward will reach the landmark if she starts, as expected, in Riga as England look to maintain their perfect start in qualifying for the 2023 finals in Australia and New Zealand.
Kirby would have likely surpassed the half-century of caps already were it not for her fight against injury, including being diagnosed with pericarditis in 2020.
The 28-year-old also quit football as a teenager following the death of her mother, who had earlier told her she would one day play at a World Cup with England.
Kirby would go on to do just that, helping England finish third in 2015 and now – with qualification for 2023 progressing well – she is preparing for a special night against Latvia.
“It’s been a rollercoaster for sure,” she said.
“But it’s a journey that I’m really proud of and one that I think looking back I probably wouldn’t change a lot.
“Obviously I’ve been through a lot but it’s made me who I am, and I’ve been able to come here, hopefully get my 50th cap, play at Wembley in a competitive fixture.
“I’m really happy about how it’s going and hopefully I can keep building.
“I’m just so grateful to be here and part of this team after the journey I’ve had. It does take you back to those memories of getting your first cap.
“It’s something I’m really happy about and has been a long time coming. Something I’ve had in the back of my mind for a while.”
She also started Saturday’s 4-0 victory over Northern Ireland at Wembley as England continued to ease through their opposition.
Their 18-0 aggregate wins in September saw the idea of pre-qualifying matches being discussed by Wiegman and, with Latvia currently fifth in Group D without a point, another heavy victory will be expected on Tuesday night.
Kirby, though, insists England will still approach the game with the same level of preparation and focus as when they take on the world’s best.
“I think internally we know that we have to play well to win,” she added.
“I don’t think it’s a case of we know, because we’re favourites, we’re going to turn up and be able to just score loads of goals.
“We still know that we have to be patient in our play and make sure that we do the right things and we treat each game the same.
“The focus is the same, the training going into the game is the same, the mindset is the same, the preparation is the same.
“So I think obviously we will be favourites going in because we’re ranked a lot higher, we’ve played higher opposition than Latvia, but we know that we have to go in with the mindset that we have for every game, whether it was a top-four opposition or a team like North Macedonia or Latvia.
“I don’t think we’re thinking too much into that. We’re just focusing on ourselves and focusing on what we can control in the game.”