@Fishwishy People remember the first human in space.
You think? Like the vast majority of people who grew up in the west, I had heard of Neil Armstrong a long, long time before I heard of Yuri Alekseyevich Gagarin. I've seen numerous situations, talking to adults and children, in quiz shows, at table quizes, etc. Where people answer the question of who was the first man in space with Neil Armstrong, or even Alan Shepherd. Yuri Gagarin is barely a footnote in western history unless someone is particularly interested in space travel. I'm sure that in Russia and Eastern Europe he is extremely well known.
However back in 1963 Valentina Tereshkova was a world wide celebrity following her solo space flight. She travelled the world, met with Queen Elizabeth in 1964, hosted the International Women's Conference, was an honoured guest at sporting competitions all over Europe. However, quite quickly, news of Tereshkova was quietened in the west, especially following the death of Theodore Freeman in training in 1964. Nasa did not want to risk a woman being killed in training or space. So few if any of us learned of Valentina Tereshkova as children. This isn't true in Russia however where Tereshkova has had lasting notoriety and fame, a long and highly successful military career, trained numerous cosmonauts, has held a seat in the state Duma since 2011 as she went into politics after she retired from the airforce. She's had her face on stamps, has toys and souvenirs made of her, had songs written about her, been an Olympic torch bearer, had streets and buildings named after her. Overall, she has had significantly more awards and honours than Yuri Gargarin, though his death in 1968 is the biggest factor in that.
Most people just won't have heard of her for political reasons. Not because she was only the 12th person/1st woman in space. Like with Armstrong I have heard many, many claims that Sally Ride was the first woman in space. In the east, she had all of the recognitions and honours to which she deserved.