You are right Ramya that it was thought best that Mrs B be encouraged to keep to her room and not ranting in front of the servants. In Chapter 47: "Though her brother and sister were persuaded that there was no real occasion for such a seclusion from the family, they did not attempt to oppose it, for they knew that she had not prudence enough to hold her tongue before the servants, while they waited at table, and judged it better that one only of the household, and the one whom they could most trust, should comprehend all her fears and solicitude on the subject." Indeed, we know Mrs B is rather inclined to blow things just a little out of proportion (Mr B fighting a duel with W and then being killed, etc. ...)! To have the faithful and reliable Hill (I am assuming that she would be the logical choice - not sure she is actually mentioned in the text) attending her, lessens the chance of someone less reliable taking away the latest "news" which has had "the Mrs B treatment" (ie, blown out of proportion), and then, as usually happens with gossip (the "Chinese whispers" effect), evolves into something of even greater magnitude.