Can you use gift cards to get in?

I recently got my own membership at 18 and use my dad as the secondary one since he also does the majority of the grocery shopping. (I got it because as a new member there was some kind of Groupon deal) But I’ve always heard that Costco lets people with gift cards in so when my mom was at work and wanted to get something on her way home I emailed her a gift card and when she came home she told me that the Costco employees told her she wasn’t allowed in and when my mom asked if this was always the case they said they never allowed anyone with a gift card in. Which is weird cause she’s been there like a bunch of times using a gift card and has had no problem. I’d think this is a new policy but from the way they phrased it, it seemed like they’ve never allowed people with gift cards in.