Hiscaru 
It's alright to feel confused about the situation. A lot of us here were and are. When a person says they don't want to be friends, but behaves like they want to be friends—of course you're going to feel more confused.
It's also OK to still have some residual feelings of affection toward an ex after a breakup. If you were in an emotionally involved intimate relationship with a person, then you're going to have some recollection of good times with that person. You may feel attraction and want for some parts of that person.
She cheated on me [...]
[...] she would snapchat me from the other guys house showing me pictures of him and her together. [...]
What she did to me, was I believe, the most heartless and careless thing someone could do that was in a relationship with someone for two years.
I appreciate what this feels like. My ex too, did the first, and a similar thing to the second; but while she was in the bedroom with the third party.
Since then I assume they are a "thing" which does not bother me, as I am moving on, however, today she texted me out of the blue again.
You can move on as you were while still having some feelings of affection for someone, and while that person is trying to contact you. For example, if your long term goals are not to have an intimate relationship with someone that cheated on you, then this direction makes sense. I think what's important is not
what choice you make, but really being aware that you
have a choice on whether you want to re-enter into the drama.
Also it would help to be aware that re-entering this drama may take the form of reacting to an initiation by your ex. So from there, you own the choice you make.
I guess what I'm trying to say here is that regardless of how poorly she treated me she still texts me like we are "friends."
Why a BP does this? There's a lot of ways to look at it—but I think a simple sensible answer is that pwBPD's cannot integrate the idea that certain behaviours cause/lead to the consequence of the destruction of a relationship. Being unable to integrate this idea means that despite having behaved destructively (in your case cheating), the BP doesn't perceive a change in the relationship's state the way you and I may do.
Whilst most people would simply tell me to block her and to move on, it's more difficult than that. I honestly felt she was the perfect companion for me [...]
Do any of you lovely people have an opinion on this? If so please share it with me as I'm honestly quite confused and don't know what to make of the whole situation.
I think what might be more helpful than saying keep-away-she's-a-cheater, is for you to see her as more of who she is. You're not alone with the "perfect companion" idea. I know what that feels like, with my ex.
In the past, before a 'destruction event' in our relationships, I think we SO's didn't experience the destructiveness consistently. Hence, we came to think there's some salvage of the "wanted" or "perfect" parts of our partner. Unfortunately for us, there is a whole person we have to have a relationship with.
Therefore, I think it would be more helpful for you to get into a mindful state and truly ask yourself if perfect companion is an accurate adjective for you to use for her. There's no right or wrong answer. Then perhaps we take it from there and you can make your own choice.
Enjoy your peace.
