In New England right now, the most likely thing for a young mother to have died of is an opiate overdose. There have been more than a hundred overdose deaths so far this year.
As for the isotope analysis -- the rumor around here is that there was something quite unexpected in the results and that's why they're doing more research and more testing. This is the first thing they've had that they haven't immediately given out all of the details for, so I'm really hoping this is the break they needed. (fingers crossed, knock on wood,
raying
One of the TV news stories last night did mention that yes, if (for example) you live in California but only drink Poland Springs bottled water, you will have Maine isotopes in your hair etc. But they didn't include that in the story they posted on line, so perhaps they weren't quite accurate. I dunno.
There are Romani in New England, and from spring to fall there are lots of migrant agriculture and service industry workers. But when you see references to "gypsy roofing contractors," or something like that, they don't usuall mean Romani, they're more likely to be using it in the sense of people who are here today, gone tomorrow, and not available to fix problems.
Immigrants only rarely get deported in Massachusetts; in general, LE doesn't check immigration status or report to ICE.