My DD was 3.6kg born and 54cm long and fit into 0000 for about 2-3 weeks before she grew out of them. Both of my DS's never fit into them. DS1 was 4.2kg and 55cm, and ds2 was 3.8kg and 56cm. While they may have fit into them width wise, they were both waaayyyy too long to get anywhere near them. And DS2 is already now into 00. I also think DS1 was into 00 by this age too....
Maybe if you do buy some, get things without feet or seperates rather than full suits and even if bubs is a bit bigger than first thought, she will fit into them and you can just put socks on her.