The Liverpool Ladies midfielder is level with Rachel Yankey on 129 international caps but will surpass that when she takes to the field in Sunday's friendly against Sweden.
And the 30-year-old, who was given her international debut in 2001 by former England manager Hope Powell, admitted she never envisaged getting close to such a milestone.
"I haven't really thought about winning my 130th cap too much," Williams, speaking to Sky Sports, before the FA confirmed on Sunday morning that she would start.
"I'm just looking forward to training well and if Mark selects me and allows me to become that most capped player then I'll be over the moon.
"But until that moment happens I've just got to keep my feet on the floor and my head in the game and focus on what's to come.
"When I first started playing football I didn't even know we had a national team - it was that many years ago!
"So it took me a while but once I got into the setup at the age of 17 and made my senior debut - well that's what every kid dreams of.
"I guess it was something I dreamed of but did I think I would be where I am now? Definitely not, but I'm grateful to Hope Powell for giving me the opportunity to represent my country all those years ago."
Earlier this week, Williams' club and international team-mate Natasha Dowie told Sky Sports she thought the two-time FA International Player of the Year could win up to 200 England caps.
"Not me - I'll be retired by then," Williams said tongue-in-cheek when asked if she could reach her double century.
"When I don't enjoy playing, don't enjoy training and I am no longer motivated to do that - that will be the time I stop playing.
"But until then I will continue to enjoy playing and if that means England caps come with it and if that means trophies for Liverpool come with it then so be it."
Williams has sacrificed a lot in order to reach the pinnacle of the women's game, but she admitted it will have been a price worth paying when she becomes England's most capped player in history.
"Any sportsperson has to make many sacrifices, spending lots of time away from family and friends and missing out on things your mates do growing up," she said.
"But there are lots of benefits from playing, there are lot of places you get to see and things you get to do and if I get the chance to achieve this feat on Sunday against Sweden it will all be worth it."