(1) There's the thesis that non-native speakers have less impediments to master the SC, since their ear is not "trained" and used to the mistakes made in daily speech that the GMAT likes to test. I do not necessarily agree with the above, but in your case it may be relevant and prove less disadvantage than you think. Not having studied in an English speaking country could well make her much more motivated to master SC.
(2) the obvious things: the strategies that work, shortcuts, tricks that help you streamline the test taking process, things you have learned about the exam / application process etc organizational/soft stuff.
Plus you may halve the cost of study materials if you need to (and make a plan) (I personally write on the textbooks themselves and "customize" them beyond recognition
so this would not work for me).
the less obvious stuff: sharing your error logs, explaining things to each other (that would take you much more time to grasp otherwise) and by explaining - learning more efficiently.
now, obviously, most of the studying you will be doing on your own, so no reason to freak out. Just make sure the arrangement does not lull you into thinking your study time is only when you are together... this will not work - make sure you follow your own pace, use your own the time windows of opportunity, etc - studying together should be fault-tolerant i.e. if one has fallen behind it should not affect the other - if you figure out how to do this, there would be no reason to freak out
One way to make things interesting and learning effective is to get together, each solve a small batch (7-8) of questions on your own, compare the results before checking whether the answers are right; if you have differences - explain to each other why you think you are right; then check the answers, explain to each other again.
(3) "How about schedule?"
Well, I cannot be of much help with that. But as I said - most of the learning you will have to do on your own either way. Get together to do the most interesting/ tricky things and questions, explain the really unusual stuff to each other, share strategies, etc.
(My English sucks today too - and the coffee machine is broken which compounds the issue =)
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