The planter above is a 10" pot. Here are some photos of my mom's plant, which is in a larger container--maybe 14" or so.

I would pot down your begonia as the pot looks too big for it to succeed right now. I thought it might be B. barkeri but that doesn't look quite right (maybe a hybrid from the same?)

You could propagate it from your remaining leaves or your mothers too. Cutting the leaves off should cause the plant to sprout some new leaves (survival response).

Thank you! Coincidentally, I did repot it last night figuring that it couldn't get any worse. Hopefully, it was okay that I cut the rhizome in half? I also removed the 3 large leaves/stems but left the roots as they were. You're right it was entirely too large a pot, given the relatively small--but healthy--root system. I have had zero luck propagating from leaves--plant division has been the only way we've been able to get more lovelies.

B. barkeri looks close! I also found one called b. fusca and a hybrid called Caribbean Queen that look similar. But they look like they lack the leaf overlap at the petiole (is there a name for that characteristic?).

Thanks again for your feedback!

I thought fusca but then discarded that idea. Certainly not C. Queen. The bigger succulent leaves are a little more difficult to start but not impossible. The idea is to treat them like succulents (very little moisture inside but still cover them to keep humidity in) and when they start rooting then to give them more water. I first thought nelumbiifolia but then your mother's leaves look different than yours.

Here is my old C. Queen in an 18 inch pot back in 2005.

My biggest one was Lotusland and I kept it for two years - it is a monster. I was able to propagate it from leaves but it was more difficult than other large leaf begonias.

I found another name you might want to check - gigantea. At least this how I bought it - from left to right gigantea, Sophie, and a smaller version of Lotusland

WOW!!! What beauties! Yes, mom's begonia is what mine *should* look like. The cupping and chewed up edges of the leaves on mine are due to disease. I'm going to check out more images of all the ones you mentioned. The search continues! Thanks!