Busy day hun. I agree perfectly with shat bf said, but even if they have started I don't think it should be expected of you. I think they should find someone who has the time for the continuity of it or expect minor possible setbacks. I know you love her, but she is their child and therefore that responsibility really falls on them. Especially if they expect you to not do anything all day but that.
OAN how are your b & sil doing? Better still I hope. And how is your sister? And have you heard any results from your tests yet?