A 3-year old with a concept of personal space...who'd have thunk it?

A little anecdote from the catalogue that Isabel seems to be producing lately.

We were standing in line, waiting to sign her out of preschool on Tuesday. We were chatting with another mom and her daughter, my friend Shannon and her son and one of the teachers. The other little girl (M) has a crush on my friend's son (N). She asked her mom if she could hug him and her mom said that she could, after they'd signed out and she did. Then she approached Isabel for a hug. Izzy was talking to her teacher and standing kind of with her back to M. Isabel turned to speak to me and found herself about an inch from M, who had her arms splayed for a hug. Izzy jumped a little because she was surprised and immediately put her hands up and stepped back in order to reclaim her personal space. I didn't really expect this, mostly because no kids this age seem to have a concept yet of personal space. Isabel, for instance, spent the entire holiday climbing all over her grandpa, gramma and aunts, with absolutely no acknowledgment of their space, even after having been spoken to about it.
After Isabel assessed the situation, she approached M (who had kind of wandered back toward her mom) for a hug in a more respectful manner than I would have expected too (walked over, spread her arms and waited for M to come to her). Maybe she is getting the message very. very. slowly.