If you met someone online trying to tell you they need money to leave, it's a long running scam.
Just Google Ukrainian Dating Scams -there are over 1 million hits. That's how common these type of scams are
ANYONE you meet online who asks for money for ANY reason is always a SCAM. There are NO exceptions to this rule. It doesn't matter why they need money or how desperate they sound. It's called grooming and these scammers are pros at using psychological manipulation to convince their victims there is a beautiful girl in love with them, then go in for the kill trying to get the sucker to send money. They claim to need money for translators, visas, passports, internet/phone bills, plane tickets, departure tax, sick relative, etc, etc -- ALL SCAMS
If you have sent ANY money at all you need to cease contact immediately, file a police report, and report the person to the site where you met to get their profile removed as there will be 20-30 other people also being targeted
Tell your 'friend' you have talked to both the Ukrainian Embassy in your country as well as your country's Embassy in Ukraine and Ukraine International Airlines and all three have confirmed to you that citizens do not need to show money to leave and that there is not even a person at the airport they see before leaving who would have the chance to ask for money. The only people they talk to are the airline employee at the check-in desk, the security guard at the Xray machine and the gate agent when boarding
Scam
You are being scammed. Search "BTA scam" for many links and read through this website:
http://www.romancescam.com/
no. If someone says it, you are duped, it is a scam
