Long story short, I met this girl 3 years ago. The start of the relationship was rocky as I uncovered some unsettling truths which were inconsistent with what she was initially telling me. In the early days she said she had never cheated on her ex-partner and that the reason why they broke up was because of his declining mental health.
Fast forward a few months into the relationship cracks started to show. I found out that not only did she cheat on her ex, she did it many, many times and would boast about it online to one of her friends stating things like "we both cheated on our partners", "If I do it with randomers I do not know them tomorrow and my BF will have no evidence", and she was signed up to lots of kinky websites while still in the late stage of the relationship with her ex-partner and into calling the many sexual partners she had "slaves" saying things like "I have another two slaves coming over today".
Also, early in our relationship we were in my car driving and she saw a male on the side of the road and without thought said out loud "wow, hot!" referring to him being attractive. This was big disrespect and caused a rift for a couple of days.
However, since then the relationship seems to have stabilised. However, I feel like that is because we don't really do much outside of our relationship. Nevertheless, I am still very wary as one time I went on holiday during our relationship about 1.5 years into it visiting my best friend and there were some really odd behaviours of my girlfriend while I was away such as me observing her wearing lipstick on our video calls on a day she said she wasn't doing much, and another time when she was unreachable for several hours but then later said it was because she was cooking (but I doubt that).
we are 3 years into the relationship but even now I don't feel like I can fully let my guard down with her despite no recent indications of infidelity but I can't seem to erase the thought that her promiscuous past and ways she spoke about cheating with her ex-partner will happen to me.
She wants to marry me, we have met each others family, and live together. I am just unsure the extent to which she can really be a different person now to what she clearly was at the end of her last relationship. I also question whether if I entered a tough spot like her ex did, would I suffer the same fate. I question if this person is truly the one for me because of this.