Why do Christians think they do no harm by evangelizing and pushing their beliefs?

My mother, bless her heart, is a very naive and gullible person and not because she is religious. She has always been this way. Ask anyone. One day, a Christian person got a hold of her and she was 'saved'. Ok, I know some people are jumping up and down right now in glee. But wait. Now my family is all messed up because she won't stop trying to convert everyone. Friends now avoid her and my father wants nothing to do with her. She is constantly trying to convert me and my brother and stays up at night worrying about our salvation. I went to church with her just to humor her but did that help things? NO! She got even worse and became more demanding. She goes to church on almost every night of the week. She took my sister out of school and decided to 'homeschool' her. My sister cannot have friends unless they are certified Christians so she basically has no friends and can't be around her brothers because we are a 'bad influence'. Now you tell me this was a good thing.