Princess Charlotte could be the first girl to attend Eton College, it is not yet set in stone. The school has not yet announced whether or not it will go co-ed, and it is possible that they will decide to keep it as an all-boys school.
Even if Eton does go co-ed, it is not guaranteed that Charlotte will attend. She may choose to go to a different school, or she may not be interested in attending Eton at all.
It is also worth noting that Lilibet is still very young, and she may not even decide to go to college at all. She may choose to pursue a different path in life.
So, while it is possible that Lilibet will miss out on the opportunity to make history by being the first girl to attend Eton, it is not yet set in stone. There are still many factors that could affect her decision.