I seriously have no idea what's going on with her arm, here it could be Will's hand but in the parent post it's suggested to be Fabienne's hand cupping her own chest but that doesn't explain this appendage.

So in the parent post I just tagged it as her cupping her own and here have Will cupping her, that's my judgement call at least. Someone else can do their own verdict, my brain hurts the more I try to mentally map what that appendage is and what it's doing.