Hi Felicia,
May I be very blunt? Yes, TOBI can cause hearing loss. However, enzymes can cause liver disease, too. Everything we give our children to combat CF will have it's own risk of side affects. The fact is, 30 years ago children were dying in elementary school because we did not have the resources to treat lung infections in a proactive way. Today we do, thanks to endless hours of research and endless donations from supporters of the CF Foundation. I realize your daughter is not showing any major symptoms, but the pseudo is there. Take the TOBI, eradicate it, and hopefully you won't have to worry about it for a number of years. The only other option is to not treat it, let the pseudomonas have a field day in her lungs, and then always wonder if you were aggressive enough.
Good luck making your decision, and I hope your daughter is pseudomonas free very soon!