Should my girlfriend forgive THIS lie AGAIN? Or what can I do to get her back?

I understand her being upset with you for lying to her when she directly asked you. However you slept with this other woman before you two were together. To me what you did in your past before we became a couple is none of my business. If she were to ask you a general question like how many woman have you been with then sure, however her wanting to know which woman you slept with that lives in the same town... it sounds like she wants to keep that in her pocket just in case anything ever happened. Also she might be asking to see if the woman you did sleep with is more attractive than she is. If she's not then nothing to worry about. If I were you I would sit her down and tell her the reason you didn't say anything about the other woman was you didn't want her to be uncomfortable around someone she knew. Yes I understand this hurts but you have to stop lying to her. If she asks you someone ask her even if the truth hurts do you still want to know. Good Luck!