Is this normal or is child abuse happinging here?

Long story short my husband just got every other weekend with his 2 year old daughter (every weekend for the first 2 months). It has taking 2 years because we tried to work things out with the mother for a year and only got to see her a few times so we took her to court and then court took a year because the mother keep rescheduling appointments.

Anyways the mothers boyfriend who she has been with since a few months before my step daughter was 1. Her boyfriend has abuse charges on him from his ex wife, and my step daughter's mother and him brake up every month because in her words "he puts his hands on me". But she loves him so they stay together.

Well we have noticed some strange things with her over the last 2 months but aren't sure if it's normal or something we need to do something about and don't want to jump in if it's normal and start a big fight with her mom when things between us aren't the best right now.

Here are some things we have noticed about her.. she is 2 years old.

-She screams and cries if the bedroom door is shut and someone is in the room with her but doesn't do it to any other room.

-She screams and cries when she has to go home and begs us to take her to her Grandma's house and if you ask her is she wants to go Grandma's? She says yes and stops crying. Then when we say no you have to go to mama's but you can ask mama if you can go to Grandma's she starts freaking out again and hides her feet so you can't put her shoes on. Then when we pull up and she sees their house she starts screaming again and when she gets out of the car she tries to pull my husband to a different house. But when they open the door she walks in just fine no crying or anything?

-She screams and cries when you take her pants off but is fine when you take her shirt off.

-She is fine when you change her diaper but when you start to wipe the "middle" she shuts her legs and starts crying saying owie.

-She always seems to be red in the "middle" area. And get's rashes a lot.

-I was putting her in her car seat and the bottom clip was under her so i went to grab it and she shut her legs and cried owie don't.

-In the bath she grabbed a toy put it in her butt and said "I sit on it?" and i said no no no no and grabbed it. Then very calmly asked her why she wanted to do that and she just looked at me scared.

- In the bath she laid backwards opened her legs up and told me to pour water down there.

-In the bath she had 2 duckies and made them kiss and i said "aww their kissing" and she had them kiss me then turned one upside down and had the one kiss the the other on the bottom.

Is this normal?
A few more things is..
my step daughter comes over smelling, unbrushed hair and mismatched clothes even pjs.
She is always at her Grandma's at least a day or 2 every week overnight by herself. I understand it's her Grandma but for 2 months we had her 3 days and her Grandma had her for at least 2 a week! (Her Grandma does not have any men in her life, or friends that stay over it's always her and her granddaughter that's it).
She is scared of the dark.
She get's violent sometimes.