Hi bella_figura,
Welcome to the forum !
It doesn't look like the leaves get sunburned ...
If not, then she just needs more water. Put her in the ground (or bigger container), and water accordingly to your weather. 2 watering cans of 3 gallons (11 Liters) each in ground are really useful ... Every day or every other day ... adapt to your locales.
Give her a bit of fertilizer too. I use the blue bullets 10/10/10 or something in those ranges ( 10/6/8 for instance) . One closed handful spread all around the tree, and water afterwards to help the bullets dissolve and go to the dirt. It will take some time for the bullets to dissolve completely and that's fine. That is what you want, a bit each day to feed the tree with each watering. After a month or two, apply fertilizer again to keep both the tree and the owner happy.
As for pinching, your tree is fruiting and looks so happy, that I would let her walk her plan as she planned to. You can later shape her when dormant.
With a tree of that size, you can keep the fruits and harvest them when ripe.
Nice purchase !