"Kol Isha"

Question

Rabbi, I have a dilemma which only you can solve. Our synagoge is a modern orthodox one, with a balcony mechitza. On shabbat there is a particular woman who sings the duvening songs VERY VERY loudly with a shrill high-pitched voice that dominates the shul. The rabbi is reticent to say anything to her out of the fear of embarassing her, but I could care less. Isn't this a case of 'kol isha' and she needs to turn the volume down? Perhaps you could answer this question because I know she visits this board frequently. Thank you for your attention.