I'd expect it to hate being inside a house.

I heat my greenhouse and they weren't very happy but they lived.

To get them to flower, let them get really dry between waterings.

Yours is lovely, mine are much more scraggly.

Thanks for the responses. It took almost all summer for the plant to get lush and healthy looking so I thought that if I tried to copy the hawaiian environment (without the sun of course!) by bringing it into my garden room it might rebound sooner in the springtime. I will do what you suggest -- let it dry out between waterings. I wish I didn't lust after these wonderful tropical plants!

I doubt your house duplicates a Hawaiian environment. House interiors are fine for us cave dwellers, but they're too dark and too dry for most all plants. Our eyes adjust quickly to the relative darkness so we don't notice it, but the plants sure as heck do. And heating systems dry the air to desert levels, dehydrating leaves and encouraging mites.

A greenhouse could work, but not a house.

I have overwintered my bouganvillea in the home, east window and it did ok. I share your tropical cravings!

I kept one for a few years, overwintering indoors in the brightest spot in the house -- a large obstructed east-facing window in the living room. A south-facing window would be better. It won't be happy indoors but it'll live until next spring. It may lose many of its leaves but will recover. Consider treating it with a mild insecticide before bring it indoors as you may bring in hitchhikers.... one aphid will multiply into millions in just a few weeks. Don't forget to treat the soil & pot, also.

(I killed mine one winter when I left it out too long.)

I've overwintered mine for a couple years now the exact same way, same temps, perhaps a skosh more water. They look dead by spring but come back nicely every time.