Well, you’ve answered your own question there, haven’t you?
If you’ve bought a house that you can’t afford to live in when interest rates rise from rock bottom, and when the cost of fossil fuels rises - entirely predictably - then you’ll have to move to somewhere smaller. That is what people have always done.
The impending cost of living crisis for well paid people, like the OP’s colleague, will have been obvious for years to anyone who reads this site and has the sense that they were born with. It’s been an approaching iceberg for ages.
Example: threads about the cost of houses. Always the same. A poster complains that a lender won’t lend enough for them to buy their ‘dream home’. Others urge her to contact a mortgage broker, who can get them access to a bigger loan. Nobody stops to think, hang on, why was the lender not keen to advance me a massive mortgage at the limits of what I can afford? Can anybody ‘tied into a massive mortgage’ like the OP’s colleague really be surprised that they are struggling?
Or a poster asks whether to be untruthful on the mortgage application, to get a bigger loan, when in fact she’s planning to go part time. A chorus of approval is the response. Gotta get your dream home!
Or the endless advice to ‘stretch yourself’. Not just here, on property programmes. What do people think that the phrase means? If you are ‘stretching yourself’ when interest rates are as low as they have ever been, and when we haven’t had an oil and gas price shock for a while, what do you think might happen when conditions are less favourable?