@HobisFlower
It's eluded to in a few frames of chapter 1. It's not clearly shown so missing it wouldn't be too hard if you were to think the elder brother was just treating her roughly.
Spoiler is a small paragraph from a translation of chapter 2 of the novel stating she's his plaything.
They offered Martina to the Crown Prince as a mere plaything. The Crown Prince, intoxicated with victory, put Martina into his bedroom. Waiting for the occasion to strike, Martina held her breath and acted like a terrified mouse.
Personally I think Astina is the one inadvertently controlling the wolf curse. It seems likely the trigger for becoming human was kissing him on the mouth, and I think the trigger for him becoming a wolf again was her thinking about Theodore.
Glad to see the goodest boye is back <3 Though I feel bad for Theo. I'm starting to think of them as two entirely different...people? Entities? Maybe they can split into two separate bodies and we can have both Theo and the giant wolf.