Using a throwaway because of what I'm about to type. 

My girlfriend has diagnosed BPD. She is in therapy.  I have researched and researched, ive read lots of books, videos etc etc. The good the bad the ugly, you name it, ive tried my damn hardest to be the best loving and supportive partner i can be. 

I understand lying is not any of the 9 criteria for BPD so this is obviously not  "BPD Thing". I've been lurking on this sub so I know the topic of lying has come up quite a bit.

My girlfriend lies all the time. About loads of things. Some of it white lies however some of her lies are ridiculous at best. 

I have heard things, from other people that used to know her, that don't line up with what she tells me. Theve shown me photos,  text messages etc that evidence what she tells me are lies. I used to brush this off but its become more and more apparent her lying has been going on for years.

How do I confront her about this? I know she's lying, theres evidence she's lying about somethings. Yet she carries on as if she genuinely thinks I have no idea. 

I feel like I'm being taken for a complete mug. 

Its gotten to the point I don't know whats truth and whats not.