A housekeeper would not go to the butcher's, unless she was also the cook. Which would not have been the case in a big house like Pemberley, although it might have been in Netherfield. Hill is probably both, too.

But I don't see Mrs Reynolds going out to buy meat and fish. She's too important for that. :-)

The cook in a big establishment like Pemberley would probably send one of his underlings to place the order. The butcher would then come and deliver the goods, so the cook could judge them before actually accepting them.