Is this normal behaviour?

[Cadburydelights]

Posting here for traffic. I have a partner and her DD is 9. I find she acts very young for her age and wondered if it was normal. My DP has commented a few times she's a very young 9 year old and you wouldn't think she is as old as she is. I have a 5yo DS and her behaviour is more like his.
Few examples would be she crawls on the floor pretending to be animals and scraps and screams and roars. She talks quite babyish calls my DP mama, talks in a babyish way. Play fights with swords with my DS, pretends she's a ninja. Whenever we go out she's screaming and shouting everywhere we go. She also has an obsession with favourite colours too it's red atm so she dresses all in red or can only have items that are red.
Is this normal 9yo behaviour?

If she behaves different when she's away from your ds, it's entirely possible she is seeing him as competition for attention. She's trying to out-do a 5 year old.

If you live with partner and her dd, and your ds comes to visit what dd considers her territory then she's feeling insecure. Usually she gets full attention, but he turns up and she has to share. He's younger and does need more 'attention' than her. She's trying to claim it back by being overly childish.

If you explain your living arrangements etc, it might help people give better advice.

Her behaviour absolutely is in the realms of normal for 9, bar the screaming which obviously needs addressing.
I agree with pp though, that it does sound like you want to be told she's abnormal and that you dislike her somewhat.

Is she just playing with your ds or trying to entertain him. As you say she plays sword fights with him. Would you prefer she stops. What is wrong with calling her mum mama.

Problem is the child either acts sensible and doesn’t play with her younger sibling or which would then cause problems for you as then who entertains your child

Or she continues and gets called immature

The running and shouting are a separate
Issue
Ds and dd were like this and to a certain extent so was I when I was younger we all grew out of it

@Thingsdogetbetter

If she behaves different when she's away from your ds, it's entirely possible she is seeing him as competition for attention. She's trying to out-do a 5 year old.

If you live with partner and her dd, and your ds comes to visit what dd considers her territory then she's feeling insecure. Usually she gets full attention, but he turns up and she has to share. He's younger and does need more 'attention' than her. She's trying to claim it back by being overly childish.

If you explain your living arrangements etc, it might help people give better advice.

We don't live together so they mainly see each other EOW or the school holidays. I guess it would make sense. They both are only children so used to having full attention from me and my DP all the time.

Just sounds like an annoying 9yr old lol
She will grow out of it.

neurotypical as in no special/ educational needs ...
autism etc .. girls present very differently to boys . I presumed that's what you meant as in is it normal? Or do you think she is just naughty! ?

With screaming, I always used the line my mother used with us. Screaming is for emergencies, it's a way we can indicate that something is really wrong, we need help. If children scream all the time just in playing then how will you know if there's been an accident?

That might be a helpful and age appropriate line for her mother to take, to get a child to stop and think a little.