It sounds like your daughter has a similar shape to mine, round belly, slim hips and bum and very chunky thighs (got those from her mother,LOL). The nappies that fit her best are side snapping nappies as they have two rows of snaps and you can adjust the legs and tummy separately. Those with velcro or just one row of snaps don't fit quite right. As far a particular brands go the best fitting ones for her have been Swaddlebees pockets, they are awesome, and very trim. Also Peapods (strictly speaking they have front snaps but can also be adjusted independently), Itti Bittis are quite good even if they only have one row of snaps, Berryplush. There are also other brands that also have side snaps that I haven't tried yet.

If you're lucky Gigi will find this thread and help you. She is a fountain of knowledge.