Even Lucy our mental mangalitza didn't mind me being there for her farrowing, though once she'd had her piglets she would go for me if I went in the pen! If she won't let you touch her to see if she will let down milk, the most reliable signs of something about to happen (in our experience with OSBs and mangalitzas, anyway) are: making a definite "nest" and vulva swelling. You'll know she's definitely on the way when she's lying down and panting/grunting: hard to describe but unmistakable once seen.
Mind you, with our "first timers" I can still sometimes be up every couple of hours during the night just checking. I know they're really in labour if I offer them an apple and they don't come out to get it!
HH is right about the stout, or cider works well too!