Anyway some background story would be good, I met my gf when she was very unsure about her identity and told me that she might be poly, but we both knew that she was just trying to mimicking her ex and the typical sleep around after breaking up. Then long story short, we got into our relationship but everything keeps falling apart very quickly, because I keep finding signs that she was being unfaithful and she kept telling me before that she was very much into bdsm and having threesome all that, so when I found out that she lied to me multiple times to went out and sleep with other guys while I was at work, needless to say I snapped.

She lied both about being fully transparent, never keeping me in the dark and about her entire identity, turns out she hates rough and loves it when I'm being gentle and all her past ONS, FWBs only hurt her and she hated it, so everytime when I get rougher with her, she's always struggling because she's been a faker this entire time. It's been 6 months ever since I found out and my girlfriend is still trying to change my mind that she is not poly, she hates her past, being unfaithful disgusted her and she wants nothing to do with her fake identity, that which she built up as an attempt to impress me because that's what her past friend circle would see as being a cool strong independent woman. Needless to say she regretted it a lot for having cheated on me because she thought that I was only after her for the sex and didn't think that I'd stay for so long even after finding out proof that she cheated on me while I was at work.

That was the background, the solution from a close friend of mine is to just open up the relationship, since she lied to me and turned out to be the perfect girl I've been looking for, one who is caring, elegant and gentle who is as faithful as she can ever be, because in our opinions, she can truly be faithful if she has cheated on someone before to either be unfaithful for the rest of her life, or see the damage and be the most loyal person in the world to me, well, she's staying, but the damage has been done and I'm still seeing her as a fake softie vanilla, she's only this way because she's lying to herself and she's not truly happy.

Close friend of mine: "okok, gotcha, so you can see that she's loyal to you now, you can admit that she lied and was being unhappy, but you would rather not see it and being deluded that she's still a faker?"

Me: "yup!"

Close friend of mine: "Well then open up the relationship, look for another girl who you can trust and show you how to treat your girlfriend better. Since you both have this woke mindset that all men are trash, then just look for a unicorn and enjoy bbq evening with each other."

Then I landed here, deep down I know that it'll help my girlfriend because in my own little world, I can't treat her right and I know that I can't give her the soft vanilla treatment that she wants because I only see her as something else, so if both of us are still in love with each other and are fine with opening up to a 3 way relationship, then what should we keep in mind because we both have zero clue on things work and barely get a traditional relationship working.

Also this friend of mine is somewhat related to me so no, she's being genuinely helpful and didn't try to hint anything. We're both here because we want to save our relationship together and see this as the best solution in our situation.