Getting people to stop feeding my daughter more information than she needs - HELP!

I need a little help/insight on the situation I'm currently in. I'm just going to give the basic ideas, but I'm sure it'll end up a wall of text, and for that I apologize in advance. For context, my daughter is 8 years old.My daughter's stepmom has cancer. It is a very sad situation, but isn't life-threatening as of right now. It's quite difficult at the moment because they can't pinpoint what type it is or what treatment course to take - all they know is that it is some form of lymphoma.Well they finally decided to start treatment, but then found out on the day it was supposed to start that stepmom is pregnant. She has had fertility issues for years now, so they worked out a plan to hopefully keep the baby. However, it is very risky and is basically their only chance to conceive because the treatment course they are intending on taking will affect her fertility.I feel for her and my daughter's father as this is just a crazy hectic, stressful situation. My problem however, is that my daugher knows all of this information. She knows about all of the treatment plan details and the risks involved, the pregnancy and the fact that it's very possible that it won't happen, the genetic issues that the baby may have due to prior radiation exposure, and basically that her stepmom might not come out of this alive. And that's just the tip of the iceberg when it comes to the information that they have shared with her.When they found out that she was pregnant, they called me, and I specifically asked them not to tell my daughter yet as the pregnancy was only a few weeks along at that point, and they're still not sure of the odds.A few days later, my daughter's father called and said that they told her "because she wouldn't chill out with the questions as to why the treatment didn't happen, and needs to know why she has to behave around her stepmom". They didn't just give basic details either, they told her everything from the issues conceiving to how this is their "one and only chance" so if there is a miscarriage, there will be no baby ever.I think that this is way too much information for an eight year old to take on. She's begun acting up and not listening to anyone, and I firmly believe that it's due to the emotional distress that this information is causing her. The problem is that she lives with them. I don't have any control over the flow of information - obviously, as my request for them to not tell her things was very blatantly ignored.I don't know how to get through to my daughter's father and stepmom that this is absolutely unacceptable to me, and that they are seriously jeopardizing my daughter's emotional health. Any help on this matter is greatly appreciated. via /r/Parenting https://ift.tt/31shLvF