Boulter, fiance of Australia's No.1 Alex de Minaur who was experiencing considerably better fortune in Holland, was eclipsed 6-1 6-3 by Vekic, who will face another Briton, Emma Raducanu, in Sunday's final.
Vekic revived memories of her deep run at Wimbledon two years ago, dropping only six points on serve in Saturday's 6-1 6-3 victory over Boulter who looked flat after her stunning win against Rybakina.
Vekic, 29, will contest her first Tour-level final since she reached the Paris Olympics final in 2024. She played the villain role to perfection on the Andy Murray Arena, silencing the pro-Boulter crowd with an exhibition of precision serving and sweetly-struck baseline winners.
The vastly-experienced Vekic has seen her ranking drop to 76, three places below Boulter, after a tough season and was actually beaten here in the final round of qualifying.
Marta Kostyuk's withdrawal with an injury meant Vekic got her chance in the draw as a lucky loser and she has taken full advantage of her reprieve with a stunning run to the final, including downing former world No.1 Karolina Pliskova.
Raducanu stormed into the final after thumping American Iva Jovic 6-2 6-2 in the semi-finals on a day that saw the British No.1 play two matches at Queen's.
The weather-plagued second edition of the women's tournament at Queen's meant Raducanu had a busy day, first beating Kamilla Rakhimova 6-3 7-5 at the Andy Murray Arena in a quarter-final briefly interrupted by the King's birthday flyover, before seeing off Jovic.
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