In English, it's down to pauses...
You could say twenty plus <breathe> four times four and get one answer or say twenty plus four <breathe> times four and get a different answer.
Which is why Maths, which has no room for ambiguity, there must be rules to avoid this.
The order of calculation is fixed and been around for a long time. I have a Maths degree from before spreadsheets were around so it definitely isn't a modern thing.
And your missus is catastrophically wrong. You should tell her so. Let us know how that goes. :wink: