L.C.
My daughter had the same thing when she was the same age. She ended up with reflux from her bladder to her kidneys. Her case was serious, some aren't. She required surgery to fix it.
I would suggest seeing a urologist and at least getting a renal ultrasound ordered and possibly a VCU. I certainly don't want to overreact, but if she does have this problem it can cause kidney damage. In our case things moved very quickly due to the severity of her case. Some kids outgrow it with no problems.
If you should have any questions that I can help with, please feel free to email me.