W.P.
My first son had a problem like this and it worried me. One thing I did was take him to the doctor and come to find out he needed to get tubes in his ears. Since it took me a while to figure out that he just was not hear right, it ended up taking longer for him to speak correctly. I highly recommend that she see a doctor. The longer they wait, the harder it will be for her to learn. IF she is not hearing the sounds correctly, then she can not pronounce them. My son is now 11 and he lets me know when something is up with his ears. We have to clean them regularly to make sure there is no wax buildup in them. This is also a problem that she could have. You can get it done by the doctor, or there are some solutions that you can buy at the store. I personally like to use a cleaning tool. It seems to do the job very well and my son can tell the difference when his ears are done.
Good Luck.