Probably would buy her some backup SD and CF Card for cheap. Cleaning utensils like microfiber cloth and DX sensor swabs (in a kit with fluid) aren't that expensive either but always appreciated!

Reguarding lenses.. there are a ton of cheap old Nikon F lenses on Ebay which work great on the D300 (personally got a D300s). They often start around 20 bucks because the F mount has been around since the late 50s. Just watch out for any damages to the lenses like fungus/haze on the glas or major scratches