OK with those stats I don't think you need to rush into a new seat, as you should have a while longer in the one you already have, even taking Christmas into account. Do you know what the limits of it are? A lot of them are 13kg and 75cm but some have a bigger height allowance e.g. 83/85/87cm.
How old is she also sorry? It does make a difference, as a 4 month old with those stats would probably have another couple of months to go to reach 75cm whereas a 12mo would probably have 3-4 months left. If their head is physically still within the shell of the seat, then it's not an absolute disaster to accidentally go slightly over the height limit though would be worth changing the seat ASAP if you did notice this.
Ideally for a non isofix seat particularly with short seatbelts you'd want to be looking at one of the Swedish type ERF seats - Axkid Minikid, Avionaut Sky, Britax Safe Way M for example. They are more expensive than the Joie seats, though. If you were looking at a cheaper model for example the older Axkid Move, or Minikid 2, then they won't normally fit a child until they are around 80cm tall, roughly a year old and sitting up well.
The newer seats like Minikid 4 and Britax Safe Way or Max Space are suitable from around 6 months (min 61cm) so would be OK now, but are more expensive. Or Avionaut Sky is also one which you could use now as it's suitable from birth.