Hey there, noarguments. Not a hijack at all - exactly what this thread's for!
Marvellous idea to get your mum a wheelchair and get out and about.
I got mine from eBay, so probably very similar to what's on Amazon. It's aluminium and very light, and folds and comes apart in improbable ways. I've yet to find a car it won't fit.
On the downside, it's not spectacularly comfortable and too flimsy to do wheelies in which is a bummer.. Certainly wouldn't want to be stuck in it all day. But for an hour or two it's great - and stows neatly in cafes while I relax in a proper seat. It also has a weight limit of iirc 75kg, so that's something to watch out for.
The other thing to think about is transit vs self-propelled.
Con of self-propelled is big wheels to stow - but these are usually quick-release so not a major issue, and in fact I almost never have to take mine off.
Pro of self-propelled is that the user can pootle within shops, etc, even if a pusher does the A-to-B stuff. I would actually explode if I didn't have self-propelled, as DP has been known to stop when he is level with something on a shelf and say, "What do you think about these?"
"I don't know dear, whatever it is is a foot behind my left ear and you're talking to the back of my head. Again." So being able to reverse, adjust and spin round has stopped me actually killing him so far.
Good luck and happy days out!