Pandora REALLY needed someone to talk to.
Immortal law is actually a bit more complex than "you can only guide and/or empower mortals". If it wasn't, Pandora would have just broken it by hugging Sarah.
Fortunately, while that is basically what the laws boil down to most of the time, Sarah can has hug without it being ridiculously tragic.
Simplest reason is that Pandora doesn't want to have her talk with Adrian on a school day. She wants his work week to be over, and not to have it be something he has to deal with after a day of work.
She might also be justifying putting it off by whatever logic she can find, but my point is simply that she has logicaly reasons to choose Saturday to do it beyond plot convenience.