That won't happen. Alfonso alrdy knew Ines loves Carcel when he had that talk with her. It wasn't shown in the manhwa but in the novel he knew. It was mentioned in novel that he could see it in her eyes when they were talking so he just decided to just pretend to follow her plan until she comes around to showing her rl feelings. This whole time he wasn't even against Ines staying by Carcel. He always knew Carcel would be hurt if Ines stayed so he was upset at Ines not being serious with the relationship and keeping secrets from Carcel. Some ppl here are mad that Carcel is keeping contrceptive secret from Ines but look at Ines also keeping more secrets and even keeping secret of her mental illness. Alfonso just want them to be a good couple so he wanted her to tell Carcel about her mental illness.
correction
He always knew Carcel would be hurt if Ines DON'T stay
I've been rereading this many times and I can say that the day will come when Alfonso will be one of the people begging Ines to stay by Carcel's side cuz it would destroy his master and he's loyal so it would be painful to watch. This, of course, is if Ines ever leaves Carcel, seeing that she's now slowly opening up to him.