My daughter started speech at the age of 3 through the school district. I took her to the Kindergarten round up, where she was tested. She couldn't talk, grunted, pointed, cried, said "words" that only I could understand, hit herself and banged her head against the wall because of her frustration and inability to communicate. When she was 4 she was in Early Childhood, where they discovered she had hypotonia, which put her into OT/PT; she will graduate from OT/PT this coming week.
My daughter was very sick as a child. Fifteen ear infections before the age of 5 months and her first ear tubes. She had two more ear tubes before the age of three, adenoids out. At the age of seven, her tonsils came out.
What caused it? Her colds? The pharmaceutical drugs? The vaccinations? My having had food allergies/intolerances while pregnant, that I didn't discover until she was 8 years old? Honestly, we don't know; it probably was/is a multitude of things. Since she's had her tonsils out, she hasn't been sick. No cold, no flu, no ear infections. No, I take that back; one ear infection. In three years. You have no idea how hard it was, finishing up one bottle of medicine, only to have one day of respite before she started all over again with a new med. Of having to take a baby to the ER at night, alone, while hubby was out of town on business, because of yet another ear infection. It was, literally, three years of a living nightmare.
If only I'd have known then what I know now about the allopathic medical community...well, what's in the past is in the past. We can only move forward from now on, and that means we eat organic food, severely limit our sugar and pop and artificial sweeteners, preservatives, colorings, etc., etc., drink reverse-osmosis water from a well, and follow homeopathic and naturalistic medicine. Lots of supplements to build up our immune systems and make sure we don't have any depleted nutrients. Lots of veges and fruit, which are very good for detoxification and the B Vitamins.
When my daughter entered Kindergarten, my husband and I had had enough of the tantrums, running away, hitting herself, crying for no reason, just a ton of different things that weren't "normal." We took her to see a childhood specialist, who "diagnosed" her off the record as having Sensory Processing Disorder (it isn't in the psychiatric manuals, so she can't be officially diagnosed. However, it will be included under the umbrella term Autism Spectrum Disorders when the new update comes out in 2013.) Instead, the specialist treats her for anxiety and OCD, which she also has, and helps me figure out how to help my daughter with her sensory issues.
My daughter is very intelligent and is a straight B student. She will enter the 5th grade this fall and will still be taking Speech, but they have high hopes that next year will be her last year.
It isn't normal for a child to not be talking at the age of three. Please, try to get your sister-in-law to see that and have her daughter tested. Our school district has been absolutely wonderful in their handling of my daughter and her issues. While they concentrated on helping her with speech and OT/PT, we have been able to concentrate on helping her with her social skills, which is the problem area with sensory issues. The longer your sister-in-law waits to find out what's wrong with her daughter, the harder--and longer--it will take to help her daughter get better.
Bless you for being concerned and reaching out for help.