Boumkwo clocked 32.81sec, finishing last in the race in Chorzow won by Spain's Teresa Errandonea in 13.22sec after stepping in at the last moment to replace injured compatriot Anne Zagre, a specialist in the discipline.
No other hurdler in the Belgian team was available and in the event of a no-show, Belgium would have been disqualified.
"My team is the most important thing for me," said 29-year-old Boumkwo, dressed in tracksuit bottoms and towering over her rivals.
She had to step over the hurdles rather than jump but finished with a huge smile having secured vital points for her struggling team.
"I couldn't let it happen to lose by one point. That's why I considered taking part in 100m hurdles. There was no risk for me if I took it calmly."
On Friday, Boumkwo, who is also Belgian hammer throw champion, had finished seventh in the shot put competition played out as part of the European Games.
After 25 of 37 events and with just Sunday left on the programme, Belgium are 16th and last and face relegation to the second division.
