I don't know if the Safe Third Country agreement would apply to this, since the US wouldn't be the Third Country. Wouldn't that only apply if she went from somewhere else in the world to the US and then to Canada. She's from the US, not from somewhere else coming to Canada via the US. I think if it did she would've been deported immediately.
But yeah ending the Safe Third Country agreement needs to be a priority. They're sending people to a gulag down there FFS, it's definitely not a safe third country for asylum seekers by any stretch of the imagination.
Have you asked your doctor about Ozempic yet? Maybe you need to see a couple hundred more ads about it.