Chansey is one of the lake camps supports as both chanseys help bring in new pokemon that have lost their homes from the dangerous earthquakes that have been happening in the Eastern Caves.  However Milo can not be at the camp since he hasn't lost his home or well doesn't really have a home to go to so instead Milo goes towards the forest and rests there.

Chanseys Personality  Both chanseys seem to be really supportive of the cause to help pokemon in need of a home that they lost and also very serious when it comes to pokemon that lie trying to get their own tent or sneaking in.  So they pretty much take their job seriously.