Hi M.. I wet the bed until I was about 10 or 11. My parents were very understanding about it, and thankfully never got angry with me. Still there were times, as I got older, that I would get very embarrassed about it. I would wake up at some point and change myself. Sometimes I would change my sheets and sometimes I would put a blanket over it until the morning. A lot of times I wouldn't tell anyone, and since I washed my own things from a young age, no one would know. Believe me, this is as hard, or harder, for your daughter as it is for you!
You should probably talk to a doctor so that you have a better understanding for what's going on with your daughter. She could be sleeping very deeply and not waking up in time to make it to the bathroom. I remember there were times that I would wake up in the midst of wetting the bed, it was too late! Doctor's told my parents that some children's bodies develop slower than others. The bladder may be too small to hold the pee in through the night, or the muscles may be too weak. A medical professional may be able to provide more insight into your daughters situation.
One suggestion is to get the hospital pads, like the ones they use when you are giving birth to soak up fluids, and put them under the bottom sheet. Yes the pee will get on the sheet, but it can be washed, and used again. You should specify sheets for your daughters bed, as they will probably get stained. Yes, eventually you will have to throw them away, and probably the mattress too. But oh well, this is more common than you may think, no big deal. The worst thing that you could do is get angry with your daughter, and make a big deal about it. You could do more damage psychologically than you know. I'm sure she doesn't understand why she can't be normal, or like the other kids, especially if she has sisters and/or brothers (I am the youngest of three and neither my sister nor my brother had this problem). As I got older I was afraid to spend the night at my friends houses because of this problem. It was a very hard thing to deal with for a long time! PLEASE be understanding of your daughters situation, it's not intentional and she needs your support and love. Good Luck!
J.