Hi Tan

Sorry Izzy is sick..
Give panadol if she is miserable, or just looks uncomfy..as Michelle said Panadol can be given at any stage. Remember that paracetamol is primarily a pain reliever, and although is does help to reduce fever it is for relieving pain so that should be the main purpose you give it for (ie. she looks miserable associated with the fever). Some babies can have a fever and still be quite happy, in that case panadol would probably not be necessary..get me??!
Look out for other symptoms as well, not just the fever, as they are the key in what treatment should be given.
I'd also be a bit careful with the readings your thermometer is giving, as 34.8 sounds very cold! I would definitely question that.
I'm sure you have a health info help line over there, maybe give them a call. (In WA it's called Health Direct, is it different over there?) or then see your GP for some advice and a chat.
There are some nasty things going around isn't there. Hope she gets better quickly..