What Causes Sporadic Attacks Of Dizziness,loosing Eyesight And Shaking Of Hand?

Hi there. I am writing regarding my girlfriend who has been having sporadic attacks of dizziness/spaced out, then completely losing her eyesight for approximately 2-3 minutes, I see her hands shaking a little also and she gets very hot. She is 25, 5ft7 tall, 63kilos, no medical history. The above symptons generally come after we have been out for an evening, thus been drinking. However whilst on holiday she's also had the above a couple of times whilst in hot surroundings, such as busy queues. I was thinking diabetes but wanted another opinion. Will be going docs obviously when home but wanted your ideas. Thanks, mark.