What should i do tell her to leave her boyfriend or stay quiet ?

Mah best friend of almost 15 yrs has this bf they been 2gther for almost 3 yrs and wen dhay first started it waz wonderful no fights or anythin. Then he started qettin jealous . Overprotective . And a pain in da a** . He would b jealous wen she waz wid her family . Dad , mom etc . Overprotective by lockin her in da house so nobody wnt see her cuz he didnt want nobody 2 see whats his like she not his trophy . He tells her wat 2 do wen 2 do it n how . She dnt even talk 2 me alot cuz he said so n i dnt like tht i knew her first. Her Bf would like alsoo kall n scream at her foor dha dumest things like yes she did things n he did 2 nobody is perfect in dhis world . 2dae she wasZ cryin in da phone because he qot mad at her cuz she waz talkin 2 his brother like wdf ? Idk wat 2 do plz help i wana tell her 2 leave him cuz he dnt deserve her at all he makes her suffer 2 much