Especially if your husband (Ethan) has been brainwashed his whole life and has no strong sense of identity.
While I'm not a huge believer in the word brainwashing, I definitely think Ethan has been conditioned to have little direction of his own. He seems to go with the flow of whomever is around him, then lash out when pushed around one to many times (like when he yelled at Olivia for not going to his brother's grave).
I suspect the truth of the credit card thing is somewhere in the middle. Kim probably bought some MLM (multi-level marketing)
tit to sell (like Lularoe) with a credit card in both Ethan's and Kim's name and he didn't object when it was brought up before hand. Olivia is not as naive as Ethan and took issue with a purchase that could hurt his credit score, since their married, it impacts her, too.
Once there was ruffled feathers, Kim probably paid the credit card back down, but Olivia and Kim can both hold a grudge and neither likes to have to say sorry.
I feel like either one could produce receipts that would support their version of events, but neither does... so that makes me think that neither story is 100% true.