I'll start with saying there is no excuse for murdering anyone.
Upon really thinking about this case and reading between the lines and the more we know of EP I think the signs were there from the beginning that the marriage was never going to work and her leaving and going back numerous times was her futile attempt to make the marriage work.
I believe she didn't just marry one person, she married the entire family plus their religious beliefs.
And no I don't believe she suddenly became converted to the religion. She did it in the hope that she would be accepted as a valued member of the family.
I don't think she ever felt valued or appreciated or accepted. Or loved.
I know this feeling because it's what I felt during my entire marriage and no amount of trying changed anything.
I think when she received the inheritance, she thought sharing it with other family members would change the way others perceived her.
Yes I think she tried to buy their affections.
Lending money to family or friends can lead to problems and even though EP said they can pay back when they could,
it can lead to family seeing you in a different light, and not the happy light she thought they would.
It could very well lead to those people wanting to keep their distance, maybe because of embarrassment out of not paying the money back sooner, rather than the feeling of gratitude and love she might have been expecting.
They do say don't lend to families
I think all this built up resentment in her, til even small signs of being left out festered away at her.