Im so so sorry for her loss. She doesn't need to bleed for hcg to drop and just bc someone is bleeding it doesn't mean their hcg will go down either. I know two women who had ectopics who had perfect b/w even at 6 wk. one even had perfect b/w until her 10-wk appt with no bleeding. The other had bleeding early but her b/w was still fine.
Maybe she had a very early m/c, but it didn't pass all of the tissue. She really should go see her OB for u/s bc if that tissue sits around too long it can get infected.