I agree. 0.5 ppm of ammonia is 0.5 ppm of ammonia, whether the ammonia comes from a fish or from a bottle.
Consider this:
1) With a feeder fish in there, you have to do numerous water changes just to keep it alive during the cycle. Even if you don't care that it dies in the long term, you at least need it to stick around while the cycle finishes.
2) With ammonia from a bottle, you can dump in a ton, and then just let the tank sit there and do its thing. There's no living creature to worry about, so there's no need to do water changes while the bacteria colony grows. So, if your gf gets stuck with a cycling tank, a fishless cycle is much less maintenance for her. Plus, the bottled ammonia method might even be a little faster than a fishy cycle, because you can let the ammonia reach quite toxic levels very quickly.
