lol n00b, she never does, i played it thru 2 times and is on my third time and she have not done that once
I've played through twice and never lost her. Did you buy the upgrade?
No need to insult the guy - Tali can most certainly die.
Link - what can happen if you don't get any upgrades, Tali's shields being one of them.
You can get around it though, by having her in your team to fight the eyeball in the cargo bay. Then it's Legion in the engine room and I presume he dies instead.