And in a separate message, she added: "love you back @Sia you're an inspiration and thank you everyone for your love and solidarity <3. (sic)"
In Sia's original claims, the 44-year-old singer blasted LaBeouf - who appeared in the music video for her 2015 track Elastic Heart - as a "pathological liar", and alleged he lied to her about being single.
She said: "I too have been hurt emotionally by Shia, a pathological liar, who conned me into an adulterous relationship claiming to be single. I believe he's very sick and have compassion for him AND his victims. Just know, if you love yourself - stay safe, stay away."
Meanwhile, after FKA Twigs' lawsuit was filed last week, LaBeouf made a public statement admitting he has been "abusive to myself and everyone around me for years".
He said: "I'm not in any position to tell anyone how my behaviour made them feel. I have no excuses for my alcoholism or aggression, only rationalisations. I have been abusive to myself and everyone around me for years. I have a history of hurting the people closest to me. I'm ashamed of that history and am sorry to those I hurt. There is nothing else I can really say."
However, the Hollywood star insisted that "many of these allegations are not true", but also said he owed the women "the opportunity to air their statements publicly and accept accountability for those things I have done".