What happened to the character, Tibby, in the Sisterhood of the Traveling Pants Books 2 and 3? And ...?

I can't remember everything, but I really love those books. Here's what I can remember: Tibby meets a girl with leukemia, who ultimately dies of it. This girl helped to set her up with brian, a guy who played dragon video games. Brian loved Tibby all along, so she sneaks into the public pool with him after hours and swims with him in her underware. Carmen's dad gets a new wife at some point, and I know that her mom has that baby. Maybe I'm mixed up a little, but I saw that you had no answers, and wanted to try and help. Maybe someone else has already answered while I was tying this, though. Anyways, those are the best books! The fourth one is really good, too. You'll enjoy it!