I hope you were able to go back and buy what you wanted. I've always had good experiences at VS or anywhere I shop for panties. I've been doing it for a decade so I know my sizes in lots of brands.
It's totally intimidating at first, I get it. At department stores (Ross, Macy's etc) I never see any employees in the aisles, so you'll have more time and space to browse at your own pace.
VS can feel way more intimidating lol because it's literally 95% underwear so there's no real "browsing" excuse like you were just lost in the store. But everyone there is always super helpful. They might approach and say "can I help you find something?" Or "do you know her size?" And you can respond accordingly. If you want to be honest then just say your buying for yourself. I guarantee they won't care. But if that's too much then just play along and say "sure what styles do you recommend.? Or " well I think she's a medium in sweatpants " and they'll be happy to help.
Remember it's their job...they're just there to make a paycheck and likely won't even remember you when by the time you leave the store lol.
