is she into memes?

I'd start with setting up the computer entirely customized for her and then just show her how to access her email account. When she clicks a link, it launches in the browser (or insert application here), and you can send her links about things she's interested in and her interest can help lead to whatever and how she learns things like scrolling and learning what to click and not to click, etc.
Start small and very simple with the most basic tools of being able to find things she's into so her own steam propels her. As long as she's not fearful or apathetic, video phone calls, messages, photos, music, reading material, etc. should be enticing enough for her to do things on her own.

But be sure to warn her that with all good things some bad must come, so basic tenets of the fact anyone can say or do anything. Karl Lagerfeld's cat is out there, but so are a lot of free roaming penises. If she can't handle that, then maybe you should load up the computer with access to and things she will enjoy, but if she's a functioning adult, she might be fine with dealing the the occasional shoe poop acquired as one walks about the great piles of human detritus as long as she knows how to maneuver.

So much of it has to do with what kind of person she is and what motivates her.
My mother is a freaking horror show and will not do anything if someone can do it for her, but somehow she figured out how to get to some clothing sites on her own and how to check my sister's photos. I don't know if she does much else but she also doesn't use the tv remote on her own, but theirs are byzantine things. She really doesn't know what's up with the phone, or phone etiquette, or etiquette--
--frankly, I'm constantly checking for signs of dementia, but damn if i'll be able to tell as she literally hears what she wants to hear. It's easier to communicate on a purely psychic level where i think of a roast chicken and she shows up with a roast chicken. Unfortunately, relationships are more than a series of chicken exchanges, although some may debate me on that.

If she's interested in anything at all and not afraid, you're gold. Fear and apathy are the enemy in all things. Everything else can be transmuted into motivation. Make it idiot proof so anything can be undone short of pouring water on it, then make it irresistible.
Relatives, friends, kitties, gossip, antique clocks, Soviet era porn, experimental German cinema, Bessie Smith--

Remote access if possible and maybe set up Dropbox so you can share files with her directly.

I'm fond of the rule of threes. She needs to do something at least three times to start internalizing it, and show her only three different things at a time.

Show her how to do something so she learns the names of things, then have her do it three times. First, you talk her through the steps, then she tries to complete them on her own while asking you tons of questions, then she does it almost all on her own while you watch and withhold prompts as if you were not right there and she clicks about to explore until you step in with helpful hints.

It takes a while to ingrain new learning, so you may need to repeat at another time.

Keep it short, so she's not overloaded.

Encourage her to write it down in her own language.

Be prepared to provide patient phone support.

Let her known she cannot break it or mess it up totally.

It's often the most simple steps, like where the on button is, that can trip up someone so make sure those are well covered.

I would suggest that you be prepared for her to not respond with anything close to your enthusiasm. If she ends up not being all that interested, you need to be able to simply accept that.

One thing that I've seen even younger people have confusion with is the difference between double-clicking files/apps locally, and single-clicking links. Invariably, they double-click everything.

Also...Patience, patience, patience. A lot of what most of us take for granted is going to be highly confusing (and, really, illogical) to an adult with little-to-no computer experience.

Mightshould has it. Also, zero in on the things that interest her. For example, I've taught a lot of older people about photos first. Even before email.

Thanks, everyone!