Tenar, we have been using the BG on DS since we brought him home and have been using the large and small insert and haven't had a problem. We had some leakage issues with a couple of other nappies as he seems to be a heavy wetter, but have had no problems at all with BG. I would suggest using the large insert, doubling it over and add the smaller one as well if you think she may need it.
DS is also 4.5kg and 56cm so a similar size to your DD and we have them on the lowest rise.