Kind of hard to tell from the pic, but it looks like you could go even larger with the pot.

That is what's called a Florist Gardenina, because it isn't grafted, so it can't go into the ground. If it's had insects, and been repotted, it's probably just stressed and suffering from shock. BTW, don't ever fertilize a plant that's just been transplanted. It can't grow while it's trying to settle its roots in, and the roots can get burned. I never fertilize blooming plants. If you feel like you must fertilize, use an organic fertilizer very sparingly.

Take the pine needles off the top. They can harbor all sorts of insects. What kind of soil did you use to repot it into? Gardenias need very well-drained soil, so I always add about 1/3 perlite to 2/3rds of a good, bark-based soil.

Florist Gardenias need SHADE. The most sun they should get is early morning sun, no afternoon sun at all. It's always best to put a stressed plant into the shade to recover. Don't cut it back. That will encourage it to put out new growth and it needs to be concentrating on making roots for the new pot. You really shouldn't pot up more than one size pot at a time, so from a 6" to an 8", 8" to 10", 10" to 12" and so on.

Put it somewhere, if you can, where you can control the water. With all this rain, it may just be drowning. Set it up on something like pot feet or a couple of pavers so it can drain freely. Don't water until it's dry a couple of inches down. Stick your finger in the pot, and if it's dry down to your second knuckle, then water, but if not, don't water. If it's been rained on, don't water. Don't fertilize again at all.

Then all you can do is wait. It may lose most of its leaves, but if the roots are healthy, they will come back.

FWIW, I put fertilizer in the bottom of a pot, mixed in with the soil before planting, so the roots will eventually reach it when they grow.

And I use seaweed extract or compost tea to water in new transplants.

Dirtygardener - thank you. I wish i had seen your message 2 days ago before i trimmed it back. I’m not giving up on her yet but i had no idea about a Florist Gardenia. obviously, i didnt know much of anything regarding gardenias. Thank you so much. I’ll keep you posted.

I can’t really tell from the picture but is it indoors? If so do you have somewhere it can be placed outside?