It's called MAKE UP. You can see the highlights on her nose in the picture on the right to make her nose appear more defined and smaller. She doesn't even need a nose job; her nose is so tiny.

Your nose can change a bit (I don't have the exact same nose than when I was 17/18) but I no longer think she's had a nose job. All the before/after picture claming conveniently use pictures where she has make up on, they never use natural pictures that show her nose is still almost the same as it has always been...

I noticed they used to contour her nose A LOT during the Britney era, that's why she looks so different during that transitional period

Y'all need to stop with this pic implying that the nose job was recent

That was her nose BEFORE her first nose job in 2001.

A better example would be this:

to

After that it's just contouring

EDIT: