I have cerebral palsy and rheumatoid arthritis so I definitely can't "do" fiddly. I've been very happy with my MVP for a battery. If weight is an issue with regard to how much she can hold, go with the itaste vv3, it has the same form factor as an ego with variable voltage/variable wattage, passthru ability, ohm checker and circuitry protection. She may not need/want any of that "extra stuff" right now apart from the circuit protection, but she won't be able to manage an ego twist very easily, so if she *ever* wants to be able to manage with a vv/vw device in the future, the vv3 or the MVP are the only options available to her at an affordable price point. (There are other affordable options but then she has to mess with batteries - more fiddling and more upfront expense.)
Re toppers... eesh. Cartos..... maybe? How is her aim when dealing with fine motor work? I dumped cartos within the first two weeks... they're expensive, and the only way I could get the carto full without getting juice down the hole was to stick a toothpick down the air hole first. Even then, I often ended up with more juice on my hands/the table than in the carto (I can't do the carto-condom fill method some use, that little adventure ended up with liquid *everywhere*). That said, my abilities and disabilities are not the same as your friend's so they may be a good option for *her*, if she can master how to drip liquid down the side, and can afford to replace the cartos when they wear out.
So, other options, what about tanks? The issue there is, vaping with tanks is in general *much* more fiddly than a good RBA/genny set up. I struggled with tanks for months because I thought I couldn't wrap coils... got dry hits, flooding, was constantly unscrewing, screwing, adjusting the silicone cap on the coil head, etc etc.
For *me* - and I stress, for *me* - it is much *less* fiddly to use a genesis or an RBA, wrap a coil, and then *leave that sucker in there* - dryburning is then as simple as yanking the wick, firing till there's no more vapor, sticking another wick through and I'm done with it, no fiddling around with screwing and unscrewing things all the time. I only build a new coil about once a month, and that's usually because I got bored.
I grew up with several friends who were affected by thalidomide or had ectrodactyly. Some of them had better fine motor abilities than others (everything from better than mine to a complete inability to grip)... so my question would be, which is easier for your friend - filling a carto, that screwing/unscrewing motion for a tank, or poking a wick through a coil?
If it's the first, then cartos, and she's sorted. More power to her!
If it's the second, maybe go with the Kanger Aerotank Mega - it seems to be one of the more reliable tanks out there, and has air flow control. I will say my Areotank Mega is the *least* fiddly tank I own so far, and the one I usually go to first for out-and-about.
If it's the last, I would bet a large amount of money that the easiest thing for her would be to use a genesis or an RBA, and then have you or some other good samaritan wrap a new coil for her every 2 to 4 weeks. If she has someone else to actually do the build, dry burning and rewicking an RBA or a genny is much easier than trying to dry burn a tank coil. It used to take me 30 minutes of creative cursing to get my tanks dry burned and reassembled... it takes me literally thirty seconds to dry burn and re-wick my RBA or my gennys.
As far as which RBAs/gennys have a lot of space to work with for wicking and won't break the bank - I like both my Tobeco Krakens and my Infinite Magma for ease of wicking, with coils wrapped around a #0 metric screwdriver so that the hole is big enough for even my crappy fine motor coordination to poke a wick through.
Definitely don't go with something like a Russian or a kayfun. (If I don't say that, I suspect some well meaning commenter will suggest one.) I tried both and traded them away almost immediately, as for me they're the worst of both worlds when it comes to *maintenance*.... in order to troubleshoot it or dry burn it, I have to take the whole bloody thing apart, just like a tank, but *unlike* a tank, I also have to build coils for the thing. If I had a butler to do all the fiddly work for me they'd be great, but for doing it myself, I need something that is *easy* to fill where the coil is *easily* accessed.
Hope that helps.
She does fine. 
