Some people have greater success introducing younger chins to older chins, and others do just as well introducing two adult chins. It just depends on what you are looking for and how much patience you have. You also need to realize that just because you want her to have a new roommate, it doesn't mean that SHE will be happy to have one. For that reason, you need to be prepared with a second set up ready to go. Even if they do get along, you should always have a spare cage on hand. Chins that have lived together for 5 or more years can suddenly turn on, and maim, each other.
If you look under the forum FAQ section, there is a thread that discusses different ways to introduce chins. Remember that you'll want to do a 30 day quarantine when you bring a new animal into the house. That means separate cage, separate room.