Q.gardenias
We are snow birds and have/had a gardenia bush for approx. 9 yrs. When we arrived here in Fl. in Oct. half of our bush was dead. It had always looked very healthy except when some sort of viney weed grew up through the middle. While we are here, I keep this vine removed but over the summer it grows up through. There has never been a problem over the summer before. The other half of the shrub was trying to come back but now it looks like it has suffered the same fate. There is no vine in it. What could have caused this?

Certified GKH Gardening Expert
Check these articles for information on gardenia diseases, especially root rot, that may have attacked your plant:
https://www.gardeningknowhow.com/ornamental/flowers/gardenia/common-gardenia-diseases.htm
http://www.clemson.edu/extension/hgic/pests/plant_pests/shrubs/hgic2058.html
Also, has anything changed in the landscape, or has there been harsh weather? Make sure your gardenia still has the proper conditions it needs to be healthy:
https://www.gardeningknowhow.com/ornamental/flowers/gardenia/gardenia-plant.htm
The vine would probably not kill the gardenia all by itself, even if it slightly weakens it through competition. The only exception is if it is a parasitic weed like dodder:
https://www.gardeningknowhow.com/plant-problems/weeds/dodder-weed-control.htm