How to overcome low self-esteem in a person?

Hi doctor,

My sister is 36 years, married, and she has four kids. She always faces problems with her husband. The same complaint is always there. He is humiliating me. He sees me as useless. He is neglecting me. He does not respect me. When I tried talking to her, I saw that her self-esteem is low and she is denying that all the time. Her marriage is about to collapse. We tried to convince her to visit a marriage counselor or a psychiatrist. But she refused. She says that all of the family is against her and we are not supporting her. She does not want a divorce nor solve any issue. She gets her full needs of self-actualization from social media educational groups that she participates in most of the time. I am afraid that she is living in her own world and refuses to have support from us. How can I help her? Or how can I wake her up as she is going to lose everything but she is unaware due to denying and blaming others? We do love her and she needs help.