Help??

My SIL got several positive tests two weeks ago and started spotting with small clots but over a few days got much lighter and stopped. Her hcg was 30, then 45, then down to 25. This was all in a span of a few days. This was also the 17th ish. They assumed chemical pregnancy. (She is slightly irregular, estimated 4w as of the 17th). Her dr stopped checking levels around the 20th when they dropped. She’s still getting positive tests. Any ideas? She’s getting a new doctor. Tysm!