You probably aren't doing anything wrong. I am originally
from Illinois but now live in Southwest Florida. Here
in Florida when the weather cools down and the days get
shorter the plumerias that are in the ground lose their
leaves. When the weather warms up the leaves will come
back onto the plants. They could be considered a tropical
deciduous shrub. When I had many houseplants in Illinois
they would be in South facing windows and not do too much
until March or April. I would leave it in the same location and water it maybe about every week or 10 days
and in time it should come back. I hope I helped a little
bit.

Gardenbysarasota...thank u for your input. I will continue to water sparingly and hope it stays alive until spring. At least you gave me hope ;)
Happy New Year!

I hope things will go well with your Plumeria have a
great New Year.

Did she come out of dormancy this year?