I thought it was a dracaena of some sort too, but can't find anything online that matches.

I have Jade Jewel, this is much streakier, and the foliage seems of a bit thinner substance than most dracaena.

Dracaena was my first thought as well. Perhaps explore Cordyline.

Not a Cordyline, it's a Dracaena. Looks a bit like 'Warneckii' but coloration is a bit off (I have both 'Warneckii' and 'Lemon Lime' for comparison).

Definitely not like any dracaena I've ever seen before, that's why my eyes immediately fixated on it in her greenhouse!

And, I take back what I said about the substance, does seem about the same. Only the new leaves feel thin.

My first thought was Costus

Costus might be the correct plant, iochroma. I just can't find any images that seem to have all the fine-line streakiness as the one I have.

Costus arabicus 'variegatus' seems the closest...just don't see enough streaks.

Perhaps this was an especially streaked sport, off of the mentioned plant donors costus.