My DD2 had speech therapy and her speechie couldn't stress enough how important it was to NOT talk the way they did or talk like a baby to them. Speaking to them in short sentences is fine if they have a problem with comprehension etc, but if they say 'dink' for 'drink' always say 'drink'.
Good point- my son has trouble with comprehension so that's why we've had to go back and shorten the sentences. It took us a while to realise he had a speech issue at all as he learns in scripts so he says really long sentences but he doesn't understand the individual words. He was actually saying over 100 words at 18 months so we didn't realise there were problems then.

In my experience, the children not talking at that age generally end up talking- I'd be looking more for her social communication skills which you've already said sound good HotI as you said she points.