You could find another demo that would let you know about all of the specials and still (in addition) order from your friend IF she lets you know, from the sounds of things that probably would not happen very often. Like you said, what you order will not make a difference to her bottom line and when (if ever) she asks why you have not been placing any orders then, in truth, you can say you did not know when she was placing them.
The only other option is to find an demo that has a blog to keep up yourself with the specials then order from your friend. But is sounds as though she might or might not be placing an order at that time anyway.
A tough spot to be in for sure when friendships are involved.