Is the wife considered sinful because her husband severs ties of kinship, even though she strives to maintain relations with his family and is keen on teaching her daughters to uphold kinship ties?

You must command your children to maintain ties with their paternal uncles and aunts, unless a verifiable harm results from it. You are not sinful due to your husband's cutting off his kin, but the method of advising him should be adjusted, such as encouraging him with the reward of maintaining kinship ties or seeking help from some righteous people.