i have a house that is worth x amount of dollars, i purchased this house on my own both with my own money and borrowing from my family. I made the mistake later down the road with my girlfriend adding her by her repeated asking and nagging to the deed. she has no monitary value in the house and was along for the ride. She left and got married and want half of my house. what can i do to protect myself.

You can't file a lien. She owns half the house, and there is nothing you can do to change the deed. If you had a written contract for sharing expenses and she owes you money, you can sue her for that money, but that doesn't get you her half of the house. Your only hope is to either hope she doesn't go to court to sue for partition (she can't just put the house up for sale), or to negotiate a settlement with her to buy her out.