That's actually a sign that she could be ready to potty train. Being able to stay dry for extended periods of time shows bladder control. Checking in with your ped never hurts though if you think there's something else at play.
Sounds like she's holding it. Have you considered potty training? 2.5 is an excellent age to start.
It's good that you're keeping an eye on your daughter's health. Since she's been drinking water and eating well, it's positive. However, if you're noticing a significant decrease in wet diapers and she's had a cold, it might be a good idea to check in with a medical professional just to be safe. They can provide the best advice based on her individual situation. It's always better to address any concerns early on.