Demi Lovato has a crush on Amber Heard.

The 'Skyscraper' hitmaker is in awe of the bisexual 'Rum Diary' actress - who is engaged to Johnny Depp - and thinks she is one of the most beautiful people she has ever seen.

Asked who her girl crush is, she said: ''I love Amber Heard. She's so gorgeous, it's ridiculous.''

Demi is a vocal campaigner for gay rights and revealed at Logo TV's Trailblazers event earlier this week that her late grandfather was homosexual and came out in the 1960s.

Though he died long before she was born, the 21-year-old star is convinced she has inherited her opinionated ways from him.

She told E! News: ''It makes so much sense as to why I feel so connected to standing up for what I believe in.

''When I heard the word 'trailblazer,' I automatically thought of my grandfather and him coming out in the '60s. It's very powerful. I couldn't be more proud of him.''

Demi recently filmed the video for her new single 'Really Don't Care' at Los Angeles' Pride event and says the track's meaning has changed for her since it was first written.

She said: ''When I originally wrote it, it was a break-up song.

''But now I have sung it so many times that it kind of no longer has a significance in that sort of way. When I sing it, I always want to inspire and empower. I thought what other people could relate to really not caring what people think. I thought of bullies and the LGBT community who are constantly scrutinised. What better place is there than L.A. Pride to celebrate who you are and not really caring what people think?''