Tea tree would be fabby! Has she looke at etsy or notonthehighstreet. She could sell via the interweb.
Bin there, tried that, too much grief. She prefers it as a hobby without the pressure of people wanting, wanting,wanting. Anyway the stuff she makes is simple and the Yanks have gone all fancy with it and people no longer look for purity. They think what they are getting is natural but it isn't. Her process involves no caustic soda (which most soap making uses) and no animal testing etc. BUT that comes at a cost and making in small batches the selling price reflects the cost.
Question most often asked was "Why is your soap £5 when I can buy glycerine soap in Boots for 50p?"