Is it wrong for the boss of a store, tell their worker that they cannot serve family or friends?

My aunty Jessie works at a Red Apple store, and her boss just told her that she is no longer allowed to serve family or friends.....Which pretty much sums up everyone who goes there!!!!!!!!!!!!!!!! She is my 3rd cousin, not really my aunty! And she is friends with everybody! She's 65 years old she is not screwing around on the job, sure she may joke around with a costomer but she is very professional.....I think her boss is losing business and in the wrong....Are these the real rules or is she impeding on her rights?