I just came back from a trip in Uganda (as well as Kenya and Rwanda) in January, and I felt safe the entire time I was there.
Just as you would travelling anywhere in the world, there are certain precautions you need to take such as getting the proper vaccinations, medications & consulting a travel doctor, and finding out about the area(s) that you will visit.
My travel doctor advised taking a well stocked first-aid kit, always use a mosquito net and take precautions to avoid being bitten, among other measures to stay healthy. I cannot advocate talking to a travel doctor enough!
There is corruption there, sure, but the country is much more stable than it used to be. If she goes, she should be sure to take emergency contact details, such as the phone number and address of your country's embassy in Uganda.
Many tour companies from all over the world operate tours to Uganda, and they would not be insured to do this if there were high levels of risk towards their clients. I realize this is different than volunteering, but if she is volunteering with an organization they will give her tips about safety in the immediate area that she will be in, and the country as a whole.
It is important to remember that a lot of what we see in the media is sensationalized, and also that each country is different.