You don’t need much memory for this scene, 8 GB is absolutely plenty, 4 GB would probably do just as well.
I was wrong on the number of spp. By default the scene is setup to render 64 passes of 16 spp each for a total of 1024 spp. No kidding it’s taking ages
You can set both the numbers of passes and spp on appleseed.cli’s command line:
./appleseed.cli emily.appleseed --output emily.png --samples 16 16 --passes 4
--samples 16 16, the first value is the minimum number of spp and the second value is the maximum number of spp. However this scene is not using the adaptive sampler so only the second value is taken into account.
Here it takes about 1 min 10.