I’m sorry to hear you get asked that, that’s not nice to be asked once, never mind once a week!
As above, could you swim, or maybe do exercises that don’t involve walking, such as weights, where you’re standing still, or arm weights while sitting? There are lots of gentle exercise such as leg raises (while lying down), stomach crunches, glute bridges that don’t really involve your feet.
In terms of meals, low calorie ready meals would be fine as a starter, but probably work out expensive in the long run, and can you stick with that going forward? Better to get a handle on making healthy meals from scratch, otherwise you might lose a bit of weight, then go back to your old meals, larger portion sizes etc.
Without really knowing what kinds of meals you eat now, I’d suggest:
Reduce or cut out sugary drinks, fizzy drinks etc.
Drink more plain water
Switch white bread and pasta to wholemeal
Weigh out your portions according to the packet. We often don’t realise we’re eating way more than the recommended amount of things like pasta, rice.
Reduce takeaways to once in a while (once a fortnight or less)
Reduce alcohol intake
Reduce desserts, certainly not every day
Don’t eat snacks after your dinner
Look at what breakfast you’re eating. Things like cereals can have lots of sugar in them, and again, weigh out what the box recommends for a portion. You might be surprised how many portions you’re having.
Good luck!