Anna is a lot like Magdalena in that she has been lucky that she started when the internet wasn't so big so no one notices that they are changing their ages over the year.
Originally her mother agency stated her as being born in 1985.
Interview in 2008 she says she is born in 1988
http://nymag.com/fashion/look/2009/spring/anna-selezneva/
She also says she has finished her undergraduate degree in psychology here and wants to do her advanced degree. This would meean she had finished her degree by 20 (possible). If she was born in 1990 as we say now, it means she would have finished her degree at 18. If this had happened and she was some kind of teenage prodigy we would have heard more about it in interviews.
Later in 2008 she changes and says she is a first year psychology student for Fashion TV
In 2008 her mother agency changed her age from 22 to 18.
Who cares, she looks fantastic for 30 and a lot of models lie about their age.