My sister

I don’t know where to put this but i need to talk to someone, anyone about what’s happening with my sister. it’s like a bad dream, a bad year / years. my sister is bipolar possibly, she’s 10 years old and says things like she wants to hurt other people, it’s alarming especially coming from her.. i am wounded and worried because she’s my sweet sister and only 10. why does she do this? she lives with my 2nd mother, who is by no means a bad mother but she doesn’t know how to stay single, she jumps from new girlfriend to new girlfriend instead of just raising her daughter. my sister says that she wants to hurt my moms girlfriends. yesterday morning she told my moms girlfriend that she just wanted to turn around and hurt her, but in more violent words that a 10 year old shouldn’t be saying. she’s done this before to my moms ex wife, but my moms ex wife didn’t like my sister and treated her badly. that’s why my mom left her. my mom has no idea what to do, as she’s never gone through this before. at least with me they weren’t around enough to notice when i was depressed ect, but this isn’t about me.

do they have to start locking their bedroom doors at night? in fear that she might hurt them? is she just saying words to say them?

i fear that my mom is doing damage by not letting her and my sister have alone time, i think she’s overwhelmed by the girlfriends grandchildren being there for the entire week. i saw pictures of my sister at the waterpark and she looked miserable; she just wants to spend time with her mom without anyone else being around. my mom should take time to be single and raise her daughter.

i don’t know, any advice would help, putting her in a facility away from everyone would be unfair.