I think there's pretty strong evidence after the plane incident, from his texts apologising to her and the texts between Amber and Johnny's assistant Stephen Deuters (who had been a witness on the plane):
SD: Think he's just texted you. He's incredibly apologetic and knows that he has done. He wants to get better now. He's been very explicit about that this morning. Feel like we're at a critical juncture.
SD: He wants to see you so much. He's distraught.
AH: Obviously he has no idea what he did or the extent that he did it. If someone was truly honest with him about how bad it really was, he'd be appalled. I'm sad that he doesn't have a better way to really know the severity of his actions yesterday. Unfortunately for me, I remember in full detail everything that happened.
SD: He was appalled. When I told him he kicked you, he cried. It was disgusting. And he knows it. He's a little lost boy. And needs all the help he can get. He is so very sorry, as he should be.
I mean I guess hitting rather than kicking but those messages are pretty damning to me.
This was the last text in that exchange I believe. Maybe not as conclusive since it's her word alone but it sounds like she's referring to something he is already aware of:
AH: He's done this many times before. Tokyo, the island, London (remember that?!), and I always stay. Always believe he's going to get better...And then every 3 or so month, I'm in the exact same position.