Yeah, it's certainly big. I had to transfer from one airline to another there, and it was a bit of a pain (there was a long walk involved that included crossing the parking lot).
I guess if she knows how to recognize where she's coming from and where she needs to be in English then she should be good to go for the most part. If you could it would be a good idea for you to learn her itinerary so that you can smooth out any trouble spots for her before she leaves, like making sure she knows how to ask how to get where and understand the answer. If her English reading comprehension is good, then she should be alright, like Misa said, but it's always better to make sure she knows exactly where she needs to be ahead of time to avoid any confusion and a possible missed flight. Trust me, those aren't fun.