Kudos for acknowledging that this will be tough for your DIL, and wanting to help! I wish my MIL felt the same way!

There've been lots of great suggestions here so far, but I'll add something that, while probably trivial, really drives me nuts.
If your daughter-in-law cooks/bakes something that you're not familiar with/haven't seen before, when she tells you what it is, just accept it! As an example, on Easter morning, I got up extra-early to make cinnamon rolls (
http://en.wikipedia.org/wiki/Cinnamon_roll. Everyone enjoyed them, but I had to spend all morning listening to people try to rationalise what to call them. 'Oh, it's sort of a doughnut.' 'It's kind of like..'
Yes, it
is 'sort of' 'kind of' like a doughnut or pastry or any number of other things. But what it
actually is, is a cinnamon roll. Why was that difficult to grasp?
I know it seems silly, but it was just infuriating, and made me feel very homesick and unappreciated.