This sounds like a difficult situation and is definitely an issue because people with severe asthma cannot live with anything they are sensitive to. It's also understandable that you do not want her to be angry. I know this may be very difficult, especially considering the pregnancy, but it may be best to try to find a way to move out of the house, in order to have your own space.
This is the only way to live the way you want to live. It sounds like your mother wants to help but she may not understand the severity of this or the fact that he absolutely cannot handle any of these fragrances. This is her house and it's possible that she will try to hold her ground or simply become miserable if she isn't allowed to have them.
The only other way you might word this is talking to your fiancee's doctor or your doctor and try to come up with a medical note that explains why he or your unborn child should not be exposed to these chemicals. However, long term, she may not want to live this way or may not realize that all products like this have to go.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.