It marked a stunning turnaround having been 2-0 and 0-40 down in the match before winning 12 of the next 13 games.
It made her the third teenager into the last eight in New York but another, Leylah Fernandez, said she had not been taken aback by her run to the quarter-finals.
In contrast, Raducanu said: “I think everyone is on their own trajectory. Personally, I am surprised that I’m here. I didn’t expect it – I knew I was doing a lot of great work that would pay off some day but you never know when.
“I’m super appreciative of the moment. Yeah, having to be here in the US Open quarter-finals after not playing for 18 months is just absolutely incredible.”
She has now won seven matches in all at Flushing Meadows after three qualifying wins and four victories in the main draw. She faces Olympic champion Belinda Bencic next and, immaterial of the result, is expected to become British No2 behind Johanna Konta at the end of the week.
Of her chances against Bencic, Raducanu said: “She has a lot of experience on the tour. She’s in great form having won Olympic gold. I’m also feeling good about my game, also confident with the amount of matches I’ve played. I feel like I’m building with each one.
“It will be an extremely difficult match. I know if I’m going to have a chance, I’m going to have to play some really good tennis. But I feel like I’m building for each match. I’m really excited to see what I can do on Wednesday.”