Citing Daria Kasatkina, who switched her allegiance from Russia to Australia last year, she said she no longer agreed with the argument that Russian athletes remained silent because of possible repercussions at home.
"There is a way if you don't agree," Kostyuk said. "I know some people who have left Russia the moment the war began, who sold all their business, who left everything behind because they just don't agree with what their country is doing to other people."
"I don't think [Daria] lives in Russia anyways, but the majority of players don't live in Russia.There is nothing that's stopping you if this is something you don't believe in.
"After four years, I think they've made it very clear whose side they are on."
Kostyuk spoke in response to being asked about Russian players including Andreeva who have said they focus only on the match and avoid political discussion.
Andreeva was asked after her 6-0 6-3 win over Romania's Sorana Cirstea about the challenges of playing a Ukrainian in wartime (without knowing then whether it would be Kostyuk or Svitolina) and replied: "For me it doesn't matter who I play.
"I really try to play against the ball that is coming at me. Usually it doesn't matter to me who I'm playing against, so I'm trying to really focus on the game and on the game plan."
"They are all grown-ups. They know what they're talking about. They know what's going on. They have phones. They have Instagram. They have news," Kostyuk said.
"I wish there was some more clear stance on what's going on, especially when your country is killing other people."
Kostyuk, the best player on clay this season, leads Andreeva 2-0 on the tour; the second win in the Madrid final a month ago.
Kostyuk didn't shake hands at the net then, following protocol for Ukrainians with opponents from Russia and its ally Belarus since the war started four years ago.
Kostyuk beat Svitolina 6-3 2-6 6-2 and dedicated Tuesday's win to her compatriots after a night in which Russia launched hundreds of drones and dozens of missiles against Kyiv and other Ukrainian cities overnight, killing at least 18 civilians and wounding more than 100 others, authorities said.
Kostyuk began the fortnight in tears on court, revealing her family home in Kyiv had almost been hit by a Russian missile, and she was initially too emotional to speak after the win over Svitolina.
"We had a very difficult night again in Ukraine, especially in Kyiv, so many people dead," Kostyuk said after she composed herself.
"I want to give this match to Ukrainian people and to their resilience. Slava Ukraini! (Glory to Ukraine!)"
"I found out early in the morning. I have a couple of friends that told me about it, who are there," Svitolina said. "Just very sad that we all have to really put up with this heaviness and pain every single day, and scared moments not knowing what's going to bring the next day."
Andreeva, 19, won her match in less than an hour. It will be her second semi-final at Roland Garros having lost to Jasmine Paolini two years ago.
With AP
