Is a woman's fear of her mother, exceeding her fear of God Almighty, which led her to contact someone to inquire about herbs despite her feeling that her money is unlawful, considered an act of disbelief that expels her from the fold of Islam, even if she repents afterwards?

There is no need to worry, for what you did does not necessitate disbelief (kufr), and this fear is natural and not disbelief, and it does not affect your marital life. Therefore, continue with marital relations. It seems you are afflicted with obsessive-compulsive disorder (OCD). You can refer to Fatwa no. 31562 to learn about its treatment methods.