I'm going to copy/paste what I just told someone else:
I am in NO WAY an expert, but have you looked into psychological reasons? Many children wet the bed, BUT, uncontrollable and constant wetting (and during the daytime) may be some serious signs of some form of abuse. My step-daughter is 11 and JUST STOPPED wetting the bed which she did because her bio-father was a child molester.
But it doesn't necessarily have to be sexual. I was raised by hippies. I'm a male but I had EXTREMELY long hair. I was "pretty" as a boy. Because of this, the kids at school made fun of me and kicked me out of the boy's bathroom, saying that I was a girl and had to use the girl's bathroom. Due to my anxiety of being teased and thrown out of the bathroom, I wet my pants at school every day during the second grade.
Those are just two examples of psychological reasons why someone may not have control of their bladder. I know your daughter isn't in second grade, and she's probably not dealing with the teasing, but she could be the victim of some other form of abuse. At the very least, look into it.
If it's not physical abuse or emotional abuse, then there's a good possibility that she's growing faster than her bladder. This actually happens. So she's consuming a normal amount of food and water, but her bladder is too small to hold all the fluid, and she has frequent urination which can lead to accidents. They have a pill for this, but I don't remember what it's called.
Hope this helps. And remember, take all responses with a grain of salt. This is, afterall, the internet.
:)
I am not sure if IC is hereditary or not. It could possibly be a bladder infection, but usually their is pain with urination. Although I have read that some don't have the common sympyoms of bladder infections and still they have one. If you could get a clean catch sample you could test with AZO that you buy at Walmart and drug stores. But she will likely need to be seen by the doctor. Has she alway constantly need to drink something? Excessive thirst is a sign of diabetes. I hope this helps a little.