Few things to address here. When bringing in a new chin to the house, you want to quarantine them away from all of your chins in a different room for at leas 30 days. This not only gives the new chin time to adjsut a little bit, but allows you to watch for any signs of illness. If by chance they have something wrong health wise, you dont want it spreading to all of your chins. - But since yours al already next to each other, your well past that.
Dont keep those cages to close to each other. You want a minimum of 6" space in between other wise they can still reach each other and possibly injure each other. Even male/females in separate cages that were to close have gotten pregnant. So they really can do a lot through the bars.
Speaking of which, check, double check, and check again. Make sure they are both the same gender. It can be easy to mistake this, and many ppl do. You dont want to pair a male and female up together.
Chances are your chin, in her cage, is going to get defensive. Right now, that is HER territory. And she will act accordingly.
The new chin might need time to adjust as well depending on how long you have had her. She has a new home, new ppl, new chins, new cage, new smells, new sounds... new everything. It can be a lot to get used to.
When your ready for intros, i would suggest searching the 'smooching' method. It has the highest chance of success compared to other methods. But nothing is guaranteed.
As for your question about the cage and should you get another one. Thats partially a yes either way (depending on what cage you have now.) Even two chins that are successfully bonded and live together, can one day have enough and turn on each other. In such a case, they both need to be separated perminity, and immiditally. Its not something you can wait around on. So you always need the ability to separate them. Whether it is a separate cage, or a cage that can be split in two (that can keep both chins completely away from the other.) - Hopefully its never needed. But you need to have it just in case.