I think your mother in law is talking poop, lol. My understanding is most kids don't "potty train" until closer to 2.
My daughter was about 23 months old when she finally gave up her diapers. we started her on the potty at about 15 months, just to let her get used to it.
My son was a bit tougher as I understand most boys are. He was about 2 1/2, maybe closer to three. We had a lot of oopses with him.
I am on #3 and hope he is closer to my daughters record.
Relax a bit let her get used to it. SHe has to have the understanding of what it is for and the willingness to use it.
Get some of those pull up type training diapers that let her feel the wet, or if you are braver the old fashioned training pants that lool like real undies.
Let her see you use the toilet.
I also had gotten the book "once upon a potty" for my kids and read to them about it. Seeing that everyone else does it seemed to help them.