This is such a lovely plant.

 

In addition to coming indoors and making adjustments to your plant's care to accommodate that change in location, Tibouchina has some special requirements during the short-day months of winter. It needs a drop in temperature to about 50 ºF so that it slows its growth considerably and takes a rest. Water should also be reduced to keep the planting medium just barely moist rather than thoroughly moist. Do not feed the plant until active growth resumes in approximately March. The plant will benefit from about four hours of strong direct sunlight, or additional hours of supplemented artificial sunlight.

 

These care adjustments allow the plant to take a rest for healthy renewed growth in the spring. Without the winter's rest, the plant is encouraged to continue to grow after it has expended most of its strength on flowering and it will produce damaged, unhealthy and vulnerable growth as a result. Pruning also encourages a plant to grow and it's best to do that in the spring, when the plant is restored and ready to initiate strong, healthy growth. Usually, you would cut back the main shoots by half and sideshoots back to two pairs of leaves each spring.

 

Ease back on water, reduce the temperature and let your plant take a rest. It has been a few months since it came indoors and is non-growth period will be a bit shorter than ideal this year. The plant may have reduced vigor for the growing season but should be fine in the long run.