What can I remove ?

Took off the stock airbox today to clean it. Just wondering if I can remove the bladder shaped plastic box that runs from the crankcase breather to the airbox ? I just pulled the crankcase breather hose off and pushed it down betwwen the frame and the engine so it will drain on the ground. Then I throught about removing the "bladder" shaped box and plugging the hole that leads into the airbox . What does this little box do anyhow ?
I won't hurt and performance will I ?
This is my daughter's bike and sometimes I notice some oil in the hose that leads out of the airbox, is this normal ? I am thinking maybe when she dumps the bike, oil has no where to go so it overflows into here. Is this correct ?
Thanks,
Raz