Sorry about the sleeping tablet misunderstanding...although I have actually heard of some cases where people do this to their pets, and worse to their children!

I have moved several times with my two cats and have had relatively good luck. They both love exploring the outside world and spend a lot of time outside during the night. They do tend to come inside if the weather is bad, fruit-bats are around, or one of the big neighbourhood toms is on the lurk. Boredom and bad weather are the two main reasons that they will actually annoy me during the night - thankfully, since I have returned from the UK the latter is not usually a problem.

It may also be the Heidi is getting used to the neighbourhood or simply has a problem with one of the other cats - Does she get into fights or show signs of actually being scared of the other cats?