Mine does too. It happens in the first few days, to be even more descriptive, it looks like a baby's diaper-thick black blood and I guess other things. I have it on the pad, and when i pee, it looks like coffee grinds when the blood comes out.
No Dr. has any explanation...i assume its old blood; why its dark and thick and obviously so clotty. Im no Dr. but thats the only think that makes any sense to me. If your aunt thinks shes pregnant, especially if you'se are worried about miscarriage/eptopic, she should go to the Dr. and also ask her about this bleeding.
My experience with spontaneous miscarriage was hemorrhaging, extreme pain, and I almost passed out-but did my breathing excerscises so i didnt. Also the blood was bright red. But everyones different so i think the best idea is for her to go a Dr. good luck

Thank you Yankee. I don't feel pregnant and I have taken a million tests, so I guess you could say I am closely monitoring things. Still it is nice to know my aunt's endo sister experiences the same thing and is not pregnant. :-)

This happens to me almost everytime I have a period. Doctor told me it's just old blood. I get coffee grind periods with lumbs. Sounds gross, but it's reality. Usually happens when I'm having issues with my endo.

Hope you start feeling better soon :)