I don't know why you say goodbye, I say hello

The other day at school, I was walking out the door and a Spanish friend of mine was coming in the door. Normally, this same exact situation in the states would be something like this: 

me: Hey, what's up?

Paloma: Hey!

But, following the trend of most of my other blog posts, Spain is quite different...And this is, in face, how the conversation went: 

Me: Hola, qué tal? (hey, how's it going?)

Paloma: Hasta luego! (See you later!) 

It's completely normal here, but makes me feel like they're brushing me off, haha. I guess they're right though, we're just passing each other so we're shouldn't be greeting one another as if were were just meeting up. I thought it was funny anyway..