Why did you say hi to her when you accidentally saw her in the parking lot? And when she looked at you "piercingly" why did you then ask her if she was all right?
Personally, if I had a huge fight with someone and then several years later pressed that someone to converse with me in a parking lot, after said someone had let me know several times that she absolutely did not want to have any conversations with me, I would not have been surprised to have a restraining order put on me.
Just sayin'
What false allegations? She said stuff to you - she is legally allowed to say whatever she wants to you! If she'd said them to the police, or your friends, or your employer...then you might have a case...but she said them to you, and only you. (Yes, I know you want to use what she said to you and only you as something to negate her RO, but that won't work.)

