Some people are simply biased against very old medications for a variety of reasons.
Elavil can cause many side effects but you are only taking a small dose. The important part is that you personally do not experience side effects.
Yes the original use was for depression and it is effective, it just has been eclipsed by SSRI medications and stuff. But it has many other uses, notably for sleep, migraine prevention, and as a muscle relaxant.
It is very dangerous in OD which is probably why your mom had to get involved.