Yeah, I'm thinking they probably grew apart. Why must there have been some type of drama?
My best friend from high school and I go to the same college, and we don't talk unless we see each other. Not because we fell out or anything, we just don't have that much in common anymore. She's an art major, I'm english. We just move in different circles. Since Charlotte spends most of her time in London doing whatever she's doing,, and Valentine's in France with her jumping, it's not implausible that they just don't talk anymore.
On a sidenote, Valentine is so adorable in that vid and she's seems really good at jumping.