What size diapers does she wear? Could she just need the next size up? How much does she drink on a regular basis? Is she soaking through her diapers at night, or just during the day? Could she be saving up at night and letting it all go in the mornings/daytime (that's a good indication that she's getting ready for potty training.... maybe not quite ready
, but getting ready). Those are all my quick thoughts on your problem. Maybe something there can help?