Is It Sinful to Say No When Obedience Hurts So Much?

Assalamu alaikum. Something heavy on my chest. I once mentioned a brother I had feelings for to my parents, hoping they’d consider him for marriage. Instead, I got insulted day and night for daring to choose someone myself. So I backed off and told my mother I don’t want to get married at all anymore. Thing is, my parents’ marriage was never good-30 years together and they still can’t stand each other, which left my mother deeply wounded. Today we argued about marriage again, and I was clear that I’m okay staying single. But tonight I found her crying, breaking down, saying everyone has let her down, including me. Would I be sinful if I still refuse marriage and disappoint her? And if I give in to please her but can’t mentally accept the person she chooses, is that sinful too? I honestly don’t know what to do.