Step 2: Water and vitamins
Pregnant women are thirsty. They need beverages wherever they go. It would be really really sweet if you could make sure that she has water. She might already be on top of this water-having need, but I guarantee you that she will forget her water bottle at least one time. If you are the one that produces a little bottle of water for her from your bag or car or whatever, you will earn yourself some hugs and you will avoid the panic and crazed behavior that happens sometimes when a pregnant woman gets thirsty and can't find water. I think it's totally an animal thing, but never go walking with a pregnant woman unless one of you is carrying water.
Vitamins. Likely, she will take some kind of supplemental vitamin while pregnant. If you can make sure that she takes her vitamins every day with maybe even just an email or text message, she will feel like she is part of a well-oiled pregnancy team.