She is more "in" his life than anyone else. She checks up on him and worries about him, even though he is a grown man. She might buy his clothes and his groceries, and do his laundry for him.
He might throw temper tantrums or party all night with people 10 years younger than him.
He expects to be taken care of and be pampered on-demand. He will happily take but never give.
Former partners end up becoming his enemies or new playmates.
It can take him six months to commit to buying a new sofa.
His "friends" consist mostly of his mom and the strangers he meets when out playing or partying.
Meaning he has a tendency to engage in an indirect expression of hostility through acts such as subtle insults, sullen behavior, stubbornness, or a deliberate failure to accomplish required tasks.
If something is even mildly inconvenient, he will resist doing it.
He spends too much money playing, partying, or chasing after women.
He blames everyone around him for everything that goes wrong in his life, even his mother if he can't find another scapegoat. It's unusual for a Little Prince to possess every one of these traits, so it can be hard to identify them.