“This week has been very, very special for so many different reasons. This one is pretty amazing, I’ve worked very hard for it, I played some incredible tennis all week.
“Today was a complete battle, with myself as well, because I was a little bit nervous. But I managed to get over the line, and that I’m very proud of.
“A lot of it was about me staying as tough as I possibly could mentally, and I managed to keep my cool and actually kind of went within myself and calmed myself down a lot. I think that really helped me, and then I started to relax and play through shots a little bit more.”
After an even start between the two, the sixth seeded Ukrainian began to get the better of Boulter, stringing multiple games together and rapidly closing in on the opening set.
Boulter fought back to even the set at 5-5, but Kostyuk regained the momentum to wrap up the first set 7-5.
Boulter then found her groove in the second, dominating on her first serve to clinch the set 6-2 and force a deciding third set.
The Briton continued her ascendancy into the third, claiming the first break point of the set en route to opening up a 3-1 advantage. Boulter broke again in the seventh game and stormed home from there to close out the victory in two hours and 13 minutes.
Both women picked up their first WTA Tour titles last year in breakout 2023 seasons.
Boulter claimed her maiden championship on grass in Nottingham last summer, while Kostyuk found victory in Austin.