anyone can talk to the person in solitary. BB solitary is just isolation from the rest of the house via a door.. but not communicating.
as far as dani telling shelly she is safe.. fine and not to worry. she can talk all she wants.. however .. when they actually do their HOH campaigning to dani she can not say I AM NOMINATING YOU or YOU ARE THE REPLACEMENT.. any other words that she used to
around what she is really going to do is fine.
most often they are already telling them in the DR who their target is and what their plan is .. so BB can monitor things.. and even then a HG doesnt have to be honest with production in the DR
bottom line.. you can say anything to anybody at anytime the rules gets blurred season to season