No matter what you are being told, certainly a 16 year old can ask themselves "I am accused of having an unfair advantage by consuming/receiving a substance that is forbidden in my sport - is there any truth to that?"
They’re giving her an answer to that question, though - most likely either by lying to her about what she was taking, or telling her that all the skaters from other countries are taking the same thing and she’s being unfairly targeted because she’s Russian. How is she supposed to know that’s not true?
If she genuinely thinks she’s a good person who would never intentionally break the rules, it would be pretty normal - especially for a teenager - not to question a narrative that supports her perception of who she is.