I actually have no clue about gardening, but figured I should ask the professionals instead !

This gardenia is very important to my mom, who planted it at our house the year after her mother died. That spring, the gardenia had its first flower open on the day of my grandmother's birthday. We recently sold the house, and my mom dug up the gardenia and repotted it because she wanted to take it with her. This morning I went to her house and saw to my dismay the gardenia is dying !! It only has a few yellow leaves yet, and I am wondering how to save it ! I know we used some mulch at the bottom to help keep the weight of the pot light, and some really REALLY old potting soil mixed with an organic peat mix of somekind (sorry best I can think of), and a plastic pot. Heard plastic pots are bad for keeping roots cool, have no idea if this is the problem or not !

If it is beyond repair, we left part of the plant at my old house which I am going to go get for her and try to revive it !

If you have any tips regarding the struggling gardenia and/or mom's memory gardenia repot round 2, please Please PLEASE help me out !