Grey's Anatomy: How can Lexie Grey be an intern only a year after Meredith was?

I just finished Grey's Anatomy season 3 and obviously it states that Lexie Grey is an intern the next season. I was just wondering how that could be possible since she would have to be 5 years younger than Meredith since Ellis didn't leave Thatcher until Meredith was 5. That would put them only one year apart. Anyway, I was just wondering so any information would be great, I am very curious.

I think Meredith took longer to get there. You always hear about when she went to Europe. That probably caused the delay, since it sounded like more than just a vacation.

your assuming that meridith went directly to med school which she didn't because she didn't want to be like her mom, she eventually went where as her sister probably went directly to med school.

Time in Grey's Anatomy has been questioned several times. We know for sure that one year takes three seasons. And also, Meredith took a year off to backpack around Europe, and it may have something to do with Lexie's photographic memory.