I have a customer that as soon as I see her walk in, I excuse myself to the back and tell the other person "Ill be right back". Fortunately, she never comes during a rush.... I dont know what I would do then.

I used to have a shift who would step in and immediately shut thay type of behavior down. Ex.: “ma’am if you don’t change your tone I’m gonna have to ask you to leave right now. You can’t treat the baristas like they’re not humans. Goodbye”. So I guess just talk to a cool shift. Tell them it makes you uncomfortable and hopefully they’ll understand. I sure as hell refuse service to people who have treated me disrespectfully in the past

I would just a shift or another partner to take her order before this person comes to you.

As a barista you can't exactly ask her to leave/refuse service, but you can absolutely stick up for yourself. "Ma'am, please don't speak to me that way." "I find your tone disrespectful." "Starbucks code of conduct requires customers to treat employees with respect, just as we do the same for you." (lol i know)

That said, it's a SM/SSV/SFM's job to see this and identify it as harassment and deal with it. You shouldn't have to deal with this confrontation alone/at all.