If mother tells child she can't get her stuff because she is moving with boyfriend to make a nice home for coming child and them both to be together what should they do

Huh? Can you rephrase that

I mean my friend wants to get her stuff so she can move in with her boyfriend and her mother is drunk all the time and said she can't get her stuff if my friend tries to get her stuff her mother will call the police

Well is it "her" stuff, who paid for it, I know when my older boys lived at home, the bed and funiture was not "thiers" it was mine, So what does she want to get from her moms ?