If I have someone on the boat who is truly apprehensive, I will hand them the mainsheet, and tell them if the boat heels too much just let this out until you feel comfortable. I had a friend of my wifes on board who was too fearful even for that, so I sat her next to me and she ended up driving. After a few minutes, all was well.
This worked really well for the g/f. She's not a huge fan of heeling, but once I put her in control of the traveler, she felt much better.