Jermaine, I would also like to add to the post by Tattered Heart and urge you to read the article here:
https://bpdfamily.com/content/Dr-Jekyll-and-Mr-HydeYou already have a diagnosis, and that is a starting point. You have already described many of the features of BPD.
You acknowledging the cheating and its setback in your relationship is also a turning point for both of you.
Many of us nonBPDs have to learn to navigate the ups and downs of a relationship with a pwBPD. You can also be a supportive ally to your GF as she attempts to reconnect with her M Reconnecting with her F may not be possible, and I hope you and she understand this.