This is a textbook example of faulty memory rather than 'Mandela' and I'll show you why-

The correct spelling of that product would be


READY WHIP


If you ask anyone (literate) to spell those words they'd get both right because you've separated the word from the product, like you did with your wife. So she's right about how to spell 'whip'.


In context, why do you think that they intentionally misspelled 'reddi'?


As a marketing gimmick. Obviously misspelled word is kind of catchy and if you're trying to get someone to buy your product over another, anything that put eyes on the product is a win. Now think this through. The advertising exec who came up with the pitch to change the spelling on the name of the product to catch eyeballs is now suddenly concerned about correct spelling of the second word? Especially when all you need to do is drop the silent 'H'? Logically Reddi Wip makes more sense than Reddi Whip.


I remember it as Reddi Wip because I was a stock boy in a grocery store back in the mid 70's and teenagers used to come in and huff the propellant out of the cans so we were always getting return for cans that didn't work, or they'd leave them in the cooler with the tops off and dribble on the nozzle. People started calling them wippits. In fact they buy the little gas cannisters and fill balloons with that gas and it's referred to as 'wippits'.

YMMV