Do you mean she has 30% of her hearing left or she has 70 percent of her hearing left. If her hearing was tested as abnormal before she turned 6 months, there is a very good change that she can have just about the same hearing as her peers by the time she is 5 with the assistance of specialists.

Here is a link to help you out with the process of getting her some help.

http://www.babyhearing.org/nextsteps.asp