I'd say the pot is too small, and that lower branch may have been sapping energy too. And the bad news is, she might not even survive re-potting, as is...
I was in a similar situation a while back: I took a cutting from the top and rooted it in water, and started over with it. You can take a second one from the branch, too. The remaining stem, I cut into lengths and pressed into compost, horizontally (Siebert mentions this technique on his site, in passing only, light on details) and you should get 2x new shoots from each node. I started them off in a tupperware container, lid on, to keep humid.
A healthy rootball is capable of shooting up new growth, so re-pot that and feed well, and you should be looking at getting at least half-a-dozen happy new plants from that sad one...!
All my cuttings go straight into a 10" pot, anything less is not worth it IME. And add some mycorrhizal fungi to them while you're at it. I keep my 'mother' in the bathroom, where she loves the humidity, and I do a rain-dance over her each time I come out of the shower. She's very happy!
But you did well to get her so tall without staking.