How do I Stay 'Momma Cat' to 5 Month Old??

Chelsea, is a 4 month old kitten. I got her around the end of May / start of June
and she was about 2.5 months old. I want to be like a mother cat to
her and ever since the day she came home, I have. But she seems to for
the most part want to be on her own. At what age do kittens want to be
on their own & away from their mother cat?? I remember when she came
home I would bring Chelsea on my bed & when she walked away from me, I
would, like any other real mother cat, pick her up and bring her
closer to me. Now though, she does get onto my lap and purr real loud.
But when she walks off from me, I will pick her up and bring Chelsea
closer but she wants to show her momma shes big enough..... so she
walks off.

What age do kittens want to be on their own? Is this normal??? How do
I show my kitten that I am her momma still???
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