Amber Heard has been keeping a low profile since the outcome of the defamation trial against Johnny Depp was announced last week.MORE: Amber Heard reveals the 'real' Johnny Depp following defamation trial resultsHowever, on Sunday, her sister Whitney Heard took to Instagram to share a defiant message in support of her.Whitney shared a picture with the hashtag 'I stand with Amber Heard' and wrote a lengthy tribute alongside it.VIDEO: Amber Heard speaks out in defamation trial It read: "I still stand with you, sissy. Yesterday, today and tomorrow I will always be proud of you for standing up for yourself, for testifying both here in Virginia and in the UK, and for being the voice of so many who can't speak to the things that happen behind closed doors.MORE: Johnny Depp seen for first time since winning Amber Heard defamation trialMORE: Lily-Rose Depp breaks silence amid Johnny Depp trial"We knew that this was going to be an uphill battle and that the cards were stacked against us.