Glasgow City set up a Champions League showdown with PK-35 after an 11-0 rout of Moldovan champions Noroc Nimoreni.
Both sides now have two wins in Group 8 after the Finnish hosts defeated Osijek of Croatia 3-1 in their qualifier.
Ireland's Peaumont United bounced back from their opening defeat in Group 5 with a 5-0 thrashing of ASA Tel-Aviv.
Welsh side UWIC, who had lost to the Israelis, were edged out 1-0 by Bosnia-Herzegovina's SFK 2000 Sarajevo, who top the group after two wins.
Amela Krso's 57th-minute strike was the difference between the sides in Sarajevo as the Welsh champions improved on their opening 5-0 defeat by Tel-Aviv.
But, unless Tel-Aviv can spring a surprise against hosts Sarajevo, Peaumont will clinch the runners-up spot should they defeat UWIC in the final round of games on Thursday.
Striker Sara Lawlor grabbed a hat-trick for the Irish champions, midfielder Julie Russell having opened the scoring and forward Stephanie Roche also hitting the net as they improved on their 4-0 defeat by Sarajevo.
Northern Irish champions Glentoran Belfast United were within 16 minutes of causing an upset against Group 3 hosts Olimpia Cluj before losing 4-2.
American striker Charney Burk put Glentoran ahead after 16 minutes, but Cosmina Dusa equalised for the Romanians nine minutes later.
Midfielder Demi Vance restored the Ulster side's lead after 74 minutes, only for striker Dusa to reply within two minutes and Alexandra Lunca put them ahead for the first time with six minutes remaining before strike partner Dusa completed her hat-trick.
Cluj, who hammered Birkirkara 8-0 in their opener, top the group and face a decider against 1° Dezembro, the Portuguese, who defeated Glentoran 4-0, having only edged out the Maltese thanks to midfielder Andreia Silvia's 17th-minute goal.
Glasgow, who started their campaign with a 3-2 win over Osijek and now lead Group 8 on goal difference, are the British Isles' best hopes of progression after their demolition of Nimorini.
From the moment Leanne Ross rounded the goalkeeper after four minutes, Eddie Black's side, who reached the round of 16 for the first time last season, were in a different class in Vantaa.
German striker Katharina Lindner finished the game with a hat-trick, while Jen Callaghan, Eilish McSorley and captain Ross ended with two apiece.
Centre-half Danica Dalziel grabbed another goal to add to the two she scored against Osijek, while striker Ashley McDonald marked her European debut by finding the target.
Next up for the Scots are Group 8 hosts PK-35 Vantaa, for whom American striker Catherine Walker could be the main danger after adding to the hat-trick she scored in their 6-0 defeat of Noroc.
Defender and captain Pirjo Leppikangas gave PK-35 an early lead against Osijek, Walker increased the lead before half-time and fellow forward Cynthia Uwak looked to have settled the game after 68 minutes.
Substitute striker Mateja Andrlic reduced the deficit two minutes later, but it was too late to inspire a fightback for the Croats.