Fishlock, 30, scored a terrific long-range strike to send Wales 2-1 up just before half-time in their 3-1 win.
"A great win is what we needed so overall it was a pleasing day for me," she told BBC Wales Sport.
"I had to try and play well and make sure we got the win that we deserve. But now I can enjoy it with my family."
She continued: "It is great and the build up was very humbling but I still had to play this game without thinking it was my 100th cap."
Seattle Reign midfielder Fishlock became the first Wales international, male or female, to win 100 caps after appearing in the friendly at Ystrad Mynach.
"The anthem was emotional, the only part of everything that I knew I would really struggle to contain," Fishlock added.
"I had Sophie [Ingle] next to me who is a brilliant person and captain and that was good for me.
"That was the hardest part and I got through it it and played my game."
Wales will play Northern Ireland in another friendly on Friday at the same venue as they prepare for the upcoming Fifa Women's World Cup qualifying campaign in September.
When asked whether Wales are getting closer to a major championships, Fishlock said:  "I truly believe that. I think we are not far from it at all with this group and [manager} Jayne Ludlow.
"There are tiny details we have to get better at but it's not something we don't already know.
"You can see from watching our performances we do control games and play some great stuff.
"We just have to be a little bit better in the final third and make sure we clean up in our 18."
Wales midfielder Jess Fishlock says she had to play without feeling the pressure of winning her 100th cap as they beat Northern Ireland.