Check whether her sink has a garbage disposal and if she ran it before pouring that mix down. Baking soda and vinegar fizz and push loose gunk around, but on a sink with a disposal the real clog is usually food scraps packed in the trap, and the fizz just breaks the surface of it. The hot water pot is probably what actually did the work in her case, since heat melts grease and that's what slows most kitchen drains. Try the hot water alone next time something clogs and see if it does the same thing, because if it does, the baking soda and vinegar are just for show. On a real clog past the trap, like hair in a bathroom drain, that mix won't touch it no matter how many rounds you do.

Ugh, take photos of any broken gear before you sign, that's your proof later.