I'd memorise a few potential comebacks.
"That's a wheelie spot" - "I know - that's why I parked in it"
"Where's your wheelie" - "Where's your manners?" or "None of your business" or (as you said) "Not all disabilities are visible and not all disabled people are in a wheelchair"
Unfortunately shopping centres, supermarkets, etc, don't often police their own disabled spaces so I'd be pleased if someone did call them out when they're misused.
That said, this woman sounds really rude and YANBU to be annoyed at her.
Someone shouted at me and my DM one day as we got out of the car in a disabled space. Something along the lines of "well you don't look very disabled do you?", just as my DM opened the boot and extracted my brother's massive wheelchair to pick him out of the back seat. DM just smiled sweetly and said "well, that's very kind of you - what about this one? Does he look disabled enough for you?". Cue a lot of blushing and hurriedly walking away!
If someone politely enquires whether you're entitled to use it, I don't have an issue, but any passive aggressive, or just aggressive, comments deserve the same in return.