Then, you can search for houses with the criteria you want with the amenities your mother wants (e.g. close to shopping, transportation, theaters, etc.)
More great information can be found through the Allegheny County website:
Even though, as an investment, the Southside and Lawrenceville have been experiencing the most growth, I would not advise living there if you are over 50.
If you want any more information, let me know. I'm all about helping out a fellow New Yorker that wants to send her mother to the Burgh.
Does your mother already live in Pittsburgh? Or is she relocating to Pittsburgh? Are you familiar with the city? Have you visited the area?
In the general sense, Pittsburgh is divided up into 4 major areas: the North Hills, the South Hills, the East (which includes the city itself) and then there is the area near the airport which is often referred to as The Parkway West. The MLS is one combined system for most of Western PA. Some agents will travel to all ends of the city to show properties. Other agents may choose to specialize in certain areas. The decision is yours as to whether you want to work with the same agent, or to contact several agents in several different parts of the city. If you choose to work with more than one agent, be sure to let the agents know.
As with any city, there are pros and cons to living in each of these areas. It all depends on what amenities are important to you and your mother (ie access to major interstates, shopping, commute time, school districts, daily traffic patterns, public transportation).
I recommend the help of a local Realtor to assist you with narrowing down the options. I also recommend visiting the city several times before making your decision. I have worked with many transferees over the years and they ended up making a purchase in areas that weren't initially where they thought they wanted to be.
If you need more help, please let me know. Good luck with your search!