The 27-year-old defeated eighth seed Lianne Tan 18-21, 21-13, 21-14 in a highly impressive performance in Kyiv.
Gilmour, who is the fourth seed, took an hour and three minutes to see of the Belgian and will now face Line Christophersen of Denmark in the semi-finals on Saturday.
The Dane is seeded seventh.
Gilmour has an excellent record in the European Championships and has twice reached the final, in 2016 and 2017, losing on both occasions to Carolina Marín.
The Spaniard, who is top seed, will meet Neslihan Yigit of Turkey, the fifth seed, in the other semi-final.
Gilmour’s performance is particularly satisfying given she was out of action for a period after suffering a foot injury in December.
An important tournament in its own right, the European Championships is also a key performance indicator ahead of this summer’s Olympics in Tokyo.