Hello spr420,
I'm really sorry that this has happened between you and your gf. Can I welcome you to bpdfamily and start by saying that what you describe in your post will be something that many members here will be able to relate to. I understand why what has happened would leave you feeling so devastated, I don't doubt you will be struggling to make sense of it all.
What brought you to this site in particular, do you believe that your gf presents with behaviours described on here. Certainly what you outline in your post can be typical of many SO's on here who become overwhelmed by close relationships and displays of intimacy, and feel the need to 'run away' sometimes emotionally, and other times quite literally because of behaviours associated with BPD.
I don't know what you still havng the key might mean, has there been any contact between you in the last week, you are posting on the Staying board, do you want to see if you can salvage the relationship/friendship?
There is plenty to learn, read and comment on by joining this forum. It is safe place that is supportive and informative.
Here is a link to get you started
https://bpdfamily.com/message_board/index.php?topic=56206 Please keep posting and let us know what is happenng so that we can support you through this.