Amber Heard's sister has claimed she "felt sick" when she learned the actress was going to marry Johnny Depp.
Whitney Henriquez said she "begged" Ms Heard, 34, not to go through with the marriage, telling her "him [Mr Depp] putting a ring on her finger was not going to stop him hitting her".
In a written witness statement in Mr Depp's libel case againstnewspaper, Ms Henriquez said when she first met the star, he seemed "very sweet" and she was "surprised how much I liked him".
The pair became close, "like brother and sister", she claimed, with Mr Depp, 57, calling her "sis".
However, Ms Henriquez also said her sister's relationship with the actor was "tumultuous from the start". Her statement said: "I wasn't aware of violence at the beginning, but I do remember Amber talking about them having big fights and being concerned for my sister.
"Amber told me that they would [verbally] fight — sometimes for days on end — and then go days without speaking to each other."
Ms Henriquez said there were "other things that also worried me", claiming Mr Depp did not like Ms Heard working and both actors would tell her about fights which began over her taking film roles.
She claimed Mr Depp would "get upset" about outfits Ms Heard wanted to wear to events and alleged he made her change into a "less revealing" dress for the Art of Elysium gala in 2014.
She alleged Mr Depp was "incredibly jealous and possessive and was threatened by her former partners and co-stars, both men and women".
Her statement said: "I was with them in Brazil in September 2015 when they had a huge fight because she and I were leaving early so she could do a screen test for.
"I remember his assistant, Nathan Holmes, and I joking about the fact we hoped she didn't get the role because Johnny would go crazy when he saw a picture of Jason Momoa, her co-star."
Ms Henriquez alleged Mr Depp was "verbally abusive, even when he was sober".
Her statement said: "He could insult her and say he loved her in the same sentence, with equal amounts of passion. I remember him often saying 'fucking ugly c***, you fat whore ... but God I fucking love you" — and things like this."
Ms Henriquez alleged she was often asked to intervene when the couple were fighting, earning her the nickname "the marriage counsellor".
She claimed she "began to notice signs of physical abuse, like bruises or cuts or burns on her [Ms Heard's] arm" and this was "early on".
She alleged she first asked her sister about it in mid-2013, and Ms Heard "always had an excuse".
The statement said: "I didn't challenge her about it initially. I didn't want to believe that this person I loved was hurting someone else I loved.
"Later, when she was more open about it —and after she left him — she apologised to me for not being honest when I confronted her, and explained she was trying to protect him."
Mr Depp denies being violent towards Ms Heard.