I don't see anything wrong with shopping during work hours. Since the onset of the internet and smart phones, everyone is at it all day! If they're not on social media that it. Times have changed ladies. Even the managers are online doing shopping, booking holidays - whatever. At the end of the day, as long as the work is done, what's the problem? When I was in management I was frustratingly micro-managed; he didn't like anyone using the internet, not even in their break. My argument was the day that the quality and/or quantity of work dropped below what I found unacceptable, I would ban it myself.
Discount is a perk of working for a retail company. Do we really begrudge people it?