She is already in large, which is the biggest size they do! At the moment, we use UDNN with the night booster and trifold insert and also boost on the outside with hemp or a WNNN also boosted with hemp in and out. She is sopping wet by morning but at least the bed stays dry.
We have a medium UDNN that we can just about get on her but it is no good for nights as it doesn't hold enough boosting now. We have been using it for daytime though and it is soaked within about 3 hours. Don't know how she does it. And I am actually having similar problems with Talia and she is only 6 weeks!