There’s no black and white answer, it’s often multi layered, built up over the years.
For instance, this is what happened to me and how my feelings are based on the behaviour of other adults in my life as I was growing up.
My birth mother had mental health issues but my father did not help to shield me from those as I was growing up so I was often the focus for my mothers temper, smacking etc despite me being a generally good kid - I grew up desperate for her approval. My father allowed her to treat me badly as it took the heat off him and he was afraid of her. He would always say to me all he wanted was as easy life. Well I was at the expense of that.
As an adult my mother died and my father immediately remarried to another woman just like her - as an adult myself now I decided that I wasn’t prepared to put up with another woman like this so didn’t have much to do with her and made my feelings clear to my father.
This enraged him as he saw it as a sign of disrespect to her (and to him) so he ‘sided’ with her. I stood my ground and so he cut me off - no contact for 6 years now.
This suited her and also him, no hassle from her over me - she ‘won’.
So you see, it’s not always as easy as taking sides - there often a backstory and that often involves the ‘child’ being repeatedly let down by the father over the years and the feelings that produces. It comes over as ‘being spoiled’ or being a ‘bitch’ or ‘jealous’ (I’ve been called all these) but it’s not, it’s backlash to the awful, sad, gut wrenching feeling that again you’ve been let down and made to feel worthless.
Those childhood feelings re-emerge and it literally brings it all back.
It’s often not what it seems