Sorry - little late to respond to this but, thought I'd share and show support anyhow. I am a parent to children with multiple food allergies. I rarely make anything with their allergens. Until we had to do the egg challenge for my eldest son, we did not have eggs in our home. When I host a party, all of the foods I serve are safe for my kids. I also request that if people bring foods that they be free of peanuts at least. I don't usually encourage people to bring anything unless my kids will not be present. Both kids are airborne, contact and ingest allergic to most of their allergens.
As an adult, I was having issues with MSG. My mom reacted the same way as your mom.. in fact, she actually added MSG to stuff for awhile to see for herself how I reacted. I would pass out. I ended up in ditches on the way home from her home more than once. After 15 + years of avoiding MSG and my mom's food, I was finally diagnosed with Narcolepsy. MSG was a trigger for it (probably since it affects the nervous system and Narcolepsy is a neurological disorder). I am not so sure even now she is 100% on board but, I haven't been to her home in 7 years due to my kids being allergic to cats. She doesn't live close either so, I really don't have the opportunity to eat her food anymore either.
I have learned what I can expect from her and what I can't. It has helped with being overwhelmed with anger and disappointment and I can just enjoy from her what she can give. Hope that helps. A.