"B" never travels more than 40 miles/day. I do not anticipate this changing much (Or at all) so route planning is unlikly to be an issue.
I got that - but 'never' is quite unlikely. What if she want's to go on holiday and has to drive to the airport, or something you can't expect. When she realises she can't use her car (and I presume it will be her only car), she'll be venting her frustration on you for recommending it. It might work, but if she has a test drive, tests it out and likes it, then that takes the weight off your shoulders.
Neither of them even has a smartphone (and by that, I mean they're not the type of person to HAVE a smartphone).
All motorway fast chargers work using the Electric Highway app from Ecotricity.
All the Local Council chargers near me use Charge Your Car (which you need to subscribe to, and pay for a RFID card).
All Council chargers in Essex are Charge Point Genie, which you access through a website, and have to get £10 credit for before you can use.
Most chargers in London are Source London - which you need to register to.
Most the chargers I've found in Sussex are Polar, which is a subscription service.
And that's just my local area. It's not like pulling up to a service station, filling up and paying. There is a lot of pre-planning required.
Batteries - depends on the car. I own my batteries, so no rental or anything daft like that. In fact, I think Nissan have just announced that you can now buy the batteries outright on their cars that have a battery lease.
Not certain about the Zoe. The older ones might all be 'rented' batteries. The model out this year you have the option to own or rent.
Insurance - my insurance is more than the TT I was driving, but then the estimated value of the TT was a less than half. Until I get my full year renewal I don't know the exact difference.
Servicing - same as any car. On my trip computer it's got the service intervals (actually exactly the same as our 2005 Nissan). My next service is due at 16000. The last service was at 8000.
They're tax free, and will remain tax free after the forthcoming change (in fact, both my cars are tax free

)