Birth mother didn't respond to my letter. What's next?

Hello, I found my birth mother and mailed a letter to her and included pictures of myself. I mailed it with delivery confirmation so I know that she did receive it. It has been more than six months and I haven't heard back from her. Her sister and multiple first cousins are on several genealogy websites but I didn't want to contact them. I thought that it would be a terrible idea to reveal her secret to them. Actually, I found them before I discovered her identity. What is odd is that I share a lot of DNA with them, especially her half sister, and none of them contacted me. Also, she has other children and grandchildren because I found the on social media platforms. She is retired and volunteers on her spare time. She has a great family. I found this information on the internet. She was 18 in the 1970s when I was born so it was a difficult time in her. The other issue is that I am biracial and her other children aren't. I understand that life would have been difficult for her and she did a great thing by putting me up for adoption. My parents gave me a wonderful life. They are deceased and I am the only child. I'm not looking for a mother/daughter relationship and I am not looking to spend the holidays with them. It would be nice if I could get to know them but if not, I would like to know more about my medical history and what happened around the time I was conceived. I would like to find my birth father. Also, I went to the doctor and a red flag came up and she wanted information about my medical history and I couldn't provide it. According to 23andMe, I have a genetic trait for a condition that could affect my children and their children in the future. I am not sure how to proceed. I was wondering if I should wait for six months (which would be a year after the first letter) and either send another letter or contact one of my siblings. I would really like some advice. Thanks so much. Jennifer