When my son was around 18 months and not being able to say X number of words his pediatrician said kids his age should be, I started to wonder about speech therapy. While his ped wasn't overly concerned (because he could understand simple directions, never had ear infections, was very social, etc), I felt some concern about getting him evaluated – though not quite sure what that concern was. Was I afraid he'd get "labled" as something if he did need therapy? When it came down to it, I saw no real con for getting him evaluated. If anything, he'd get some help; and since this was through our county's Regional Center, it was something we had already "paid into" as tax payers.
My son did end up getting speech therapy right after he turned 2, and I'm glad we went through with it. I honestly think he did a lot of progress on his own even before we started, but going to the sessions helped both of us. For him, he got to spend a couple of hours a week basically playing one-on-one with his therapist. It was all interactive play, and I never thought she pushed him – when he seemed to resist anything, she backed off. Some days he was more responsive to commands and mimicking, some days he was not. Some toys/activities he'd get into, some not so much, but I never saw her force him to do anything he didn't want to do.
And for me, what I got were ideas on how to encourage speech at home through play and throughout our daily lives. I personally thought that was great.
I'm curious as to why your mom is so disapproving about it. Maybe she had the same concerns as I did? Yes, kids do progress at their own pace, but if you get a good therapist (I'm sure there are those that do push too hard), I can't see any harm speech therapy can do.