This has happened to me once or twice before and it all came from two things: being overworked and not drinking enough water, before + during my shift. The next time this happens, ask if they've drank any water or pay attention to their workload. More often than not, it's that

Maybe they are low on iron.

i think the only problem with getting dizzy on hot bar is all the turning and movement + if she has sensory issues the smell of the espresso can become a lot after a while. when i’m on hot bar i can get kinda dizzy after a while from the constant twisting but it’s really not too bad, just depends on how busy we are

as someone who’s on bar almost every day for my entire shift, i tend to get like that as well bc i don’t have the time to take a sip of water. whenever she feels dizzy or faint tell her to go to the back and take some massive gulps of water. also ask her if she’s anemic bc ik when i don’t take my daily iron supplements i get like that but 10 times worse.