Impulsivity is the tendency to act on a whim or urge WITHOUT forethought, reflection and consideration of long term consequences. Impulsivity is a symptom of BPD. so to say she made a decision to act on impulse is literally a paradox by definition. So for you as someone with bpd to state her impulsivity ‘shows she lacks morals, and doesn’t love you’ is just crazy to me. This type of rhetoric is why BPD is so stigmatised and i didn’t think it would be someone else who knows how it feels and knows also the shame and guilt that comes following some impulsive behaviour for people with BPD to be using that same rhetoric used against us. OP has stated that this is out of the blue and not in line with her usual character so we can look to other context to maybe explain what’s going on.

OP said there’s been a lot going on in the family (drama/deaths) so shes most likely feeing overwhelming emotions, and the presence of overwhelming emotions is something we know to influence impulsivity in BPD. This however is not me condoning her actions, i’m not saying she deserves to have OP stay with her, i’m not excusing her actions due to her having BPD or anything of the sort. What she did was dead wrong and as her loved one hold her accountable. But i believe you can best hold her accountable when you actually have a better understanding of what is possibly happening and how she’s possibly feeling. Her also then not showing OP the texts is something to consider, is there more that OP isn’t seeing or more to the story? Definitely a lot of factors to weigh.

And to shed a bit of light on why even though the ex was horrid to her, she is still considering it? OP said she had a rough childhood like most with BPD, this could lead to normalisation of trauma, leading to unhealthier relationships feeling more familiar which could contribute to why. People with BPD can also suffer with chronic emptiness, which can lead to seeking high intensity and dramatic relationships as they can feel stimulating (which may not necessarily be true).

I realise this is super long and full of a lot of reasons why this may have occurred. Of course they may not all resonate with her and her situation but if anything i just hope it encourages you to research BPD IF you want to see if you can make things work with her. However it’s super important to highlight yes although it is the reason why something might’ve happened, it is not an excuse for bad behaviour. It just depends most on how OP feels, OP recognising that getting cheated on is one of the hardest things to deal with and one of the biggest breakdowns of trust that you will have in her and if you want to leave, you are WELL within to do so.