Heather Knight’s side had lost their first three games to leave their qualification hopes hanging by a thread, but the defending champions bounced back to beat India, New Zealand and Pakistan.
That meant a victory over Bangladesh would be enough for a spot in the last four and Dunkley’s 67 off 72 earned her the Player of the Match award and kept England’s title defence alive after a 100-run win.
She said: “I think it’s just a lot of belief in our changing room and a lot of fight.
“We obviously didn’t play our best cricket in the first few games. So we knew that we could come out and put on better performances.
“We’ve had a lot of belief in the group, a lot of positivity to get us through and sometimes that’s just how it goes.
“Just putting in a great fight from the girls and to get four wins on the bounce going into the semis I think it puts us in a very strong position.”
England leapfrogged the West Indies into third place with eight points from their seven group games and will face South Africa after India failed to bowl the Proteas out for under 174, which would have been enough to overtake England on net run rate.
Tidy bowling from Sophie Ecclestone, who produced figures of three for 15, restricted Bangladesh to 134 after Dunkley had rescued England from another top order failure.
Dunkley admitted England have had to do it the hard way to make it through to the next stage, but the 23-year-old reckons it will stand the side in good stead when the tournament goes down to the wire.
She added: “I think obviously starting with three losses, it does really put you on the back foot and every game does become a must-win game.
“But I think having those experiences now from those games puts us in a really good position and I think every team has really beaten everyone.
“So, it’s very open and I think there’s a lot of possibilities that could happen. It keeps it exciting, going into next week we’re very positive and have got a lot of confidence now.”
Bangladesh captain Nigar Sultana picked the positives out of a World Cup campaign that saw her side beat Pakistan by nine runs as they look to improve after facing England for the first time in ODI cricket.
She said: “From the first matches till the last match our spinners have dominated here. So, I think it was a good sign for us.
“And obviously I think we need to carry forward that in the future also. And we had a good World Cup, we have some good memories from here.
“So, we just want to look forward to playing well in the future.”