Looks like an Agave Parryi to me.

Thanks to you both! Unfortunately, I'm not sure my environment is ideal for an agave plant. I have an east-facing exposure with an overhang (from the balcony above my window) so I'm not sure it will be getting enough bright light, particularly going into winter, but I will try and supplement the natural light with a lamp.

Yeah. it would be a good idea to get a growing light setup, that way, you won't have to worry about it in the winter. When it is warm enough, just keep it outside all the time (if possible).

Thanks! Is the quality of light given off by a growing light substantially different from a good lamp? I usually have a few good lamps, and the (artificial) light in my bathroom is good and bright. Might that work well enough?

I actually have no idea if standard light is good enough. Most growing lights use red and blue wavelengths, instead of the standard full spectrum. I am experimenting with LED bulbs for growing, but I just don't know if a standard bulb would cut it. I know of a few kinds of growing bulbs that people on here use, I may give you some leads when I have time.

So I know a lot of people use T5HO fixtures and bulbs, but I prefer the LEDs for compactness and long term cheapness. T5HOs are better for larger collections because of the large and uniform space coverage.

https://www.amazon.com/gp/product/B01EMJLJN6/ref=ox_sc_act_title_1?ie=UTF8&smid=A5JXFOVY1UGE2&th=1

These are the kind of bulbs I am investing in, as I have a smaller collection and I just don't have the space for a big (and expensive) light fixture.

Very interesting. I didn't know any of that. Thanks very much. It's an odd situation, as it's really the only plant I have that I would need extra lights for (the ones I chose myself don't need full sun) and I wouldn't have chosen a full-sun plant for my current environment. I wish she had tried to match the plant to my conditions, since I can't go out and spend a lot of money on a lighting set up to keep one plant happy. And yet I know she's going to ask me about it and feel bad if it's not thriving. She expects it to do great, because my other plants do great, but that's because I choose plants whose needs I can meet! If not for her feelings, I'd rehome it with someone who has a sunny south-facing window.

I would then go with a small LED bulb off of amazon. For one plant, you could do a lot with one bulb.

That sounds workable :) I was a bit daunted by the elaborate set ups I've seen... Thanks for your help, encouragement and info. Much appreciated!