potbelly pig behaviour

Question
I have your book and it is great.  I have followed all your great advice and our little potbelly, Clover is a well behaved and affectionate little girl.  She can do all the tricks from your book.  She is now 10 months old and we got her spayed months ago.  We play alot together and she loves running between my legs and around our patio furniture like a little obstacle course. I get down on my hands and knees and crawl around with her and she'll walk beside me and underneath too.  Occasionally, when I get down on the ground to play with her, with no warning at all,  she'll lunge at my face with her mouth open.  She knocked my glasses off once and got goober all over my nose another time.  Once she bopped me so hard and quick that my nose started to bleed.  Immediately following these incidences, I always hold her snout down and say a firm "knock it off".  She knows I mean business and we go back to playing and everything is fine, like it never happened.  I am wondering what is causing her to just out of the blue and unexpectedly, lunge at my face.  When I am down at her level, could it be that she thinks I am another pig and that she has to show some kind of dominance or does she think that I am invading her space, or competing with her food or toys, etc?  I have no idea.  Your help is greatly appreciated.  I am really trying to figure out and understand what is going through her little piggy mind when she lunges at me. thanks
Andrea

Answer
Pigs will attack humans to show dominance if they get down low, to the pig height  level. They feel safer to attack.
Best to stay higher or find out what is bothering the pig......other pigs, dogs?
It is GREAT you have taught her all those tricks!
Not easy......congrats!
Priscilla