Vaada is the main focus of the love triangle so Virat breaking the vaada will not happen anytime soon. I don't think Sai cares about his Vaada to Pakh as long as he is ready to move on and give their relationship a chance. She will expect him to communicate this to Pakhi but the main barrier is not Vaada but Virat not having feelings for her.
I don't think she doesn't know the progression in what he is feeling for her. She is aware. More than Virat. But she is also bound strictly by her own promise to him that she will not expect any spousal things from him. I thought that dinner feeding scene, where she goes teary eyed was exactly for this. She could see what he was doing right after "Mujhse pyaar nahi karti?" and she felt helpless in that moment where she knew they are in a mess. She didn't want him to stop feeding her but she didn't know what to make of it and in the end, she chose to live that moment. She brought up Aaba but her tears were for that fleeting pining she felt for a "normal" relationship. Now, only if he tells her, "You can expect things. It is your right." That's all.