Help Bougainvillea desparately needs saving

Hello.

I recently moved into a property where one of its main features was a spectacular indoor conservatory bougainvillea. The previous owners told us it was hardy and did not need much looking after and they didn't do much for it.  Not being that green fingered I noticed there was sap coming off the plant but thought maybe that was normal and during the winter cold snap we lost our heating for a period of time. So this very spectacular bougainvillea was attacked severely by white fly and cold. 

We have now chemical sprayed it twice but I would say the whitefly have been there for about 7 weeks. It has lost nearly all it leaves and is now shedding new growth too. The plant originally had many flowers and full foliage even throughout the winter and it creeps around the whole ceiling of conservatory. It now looks very sad and ill and it is just tragic to see her in such a bad way.

If there is anyone who can advice on any miracle way that we can bring this beauty back to life I would be eternally grateful.