Flax seeds can make a simple all natural personal lubricant thanks to their soluble fiber content.
Have you ever tried putting flax seeds in water? The soluble fiber in flax seeds will dissolve into the water and make it somewhat slimy. This slime is very slippery and makes a great personal lubricant for those of you really serious about getting strange chemicals out of the products you use. Many commercial personal lubricant ingredients contain dubious chemicals like polyvinyl alcohol, a polymer also used to make rubber cement. Flax makes edible personal lubricant is water based, which makes it a condom safe lubricant as well. If you use organic flax seeds you will even have an organic personal lubricant.
I don't remember where I originally found this. Its a very interesting project for you and your sweetie.
To make this all you do is put about a tablespoon of flax seeds in about a cup of water. Wait until it gets to your desired slimyness, and strain out the flaxseeds.
...and there you have it. Homemade lube. Do it for your health.