The official response.
via Games Workshop 40.000 Facebook
https://www.facebook.com/Warhammer-40000-1575682476085719
Woah, we knew she'd be popular, but selling out in under 5 minutes is impressive even for a Battle Sister of her status.
Don't worry though, we're making more, so you'll all be able to add this new heroine of the Adepta Sororitas to your army.
Select 'Email Me', and you'll be amongst the first to know when she's back in stock: