Only maturity will calm her down. She is still very much a puppy. Spaying does not calm them down and there is no need for her to have a litter before she is spayed. You may have more health problems if you have a litter than if you don't. Also, the expense of having a litter is very high. Do you plan to do all your health testing before you breed her? If not, you should. Health testing alone amounts to a lot of money. Then there is the expense of having to look for a suitable male to compliment your female. Then, there are sooo many things that can go wrong with the birthing process. You may run into health problems there and afterwards. You will have the expense of raising the litter of pups, finding them good homes, ensuring that they are well taken care of. You should also be responsible for your pups that you place their whole lives. Are you willing to take the puppy (dog) back in the event something happens to the home you have placed it in??
There are so many things to breeding your girl that it really is not worth it to her to have to put her through it if all you want is a calm dog. Age and maturity will take care of that. Some Basenji's are just very vocal. My puppies that I have placed always scream when they figure out who I am. It gets quite embarrassing when I am out at a show and my puppy people come by to see me. Everyone turns to look to see who is slaughtering the basenji! It's not unusual for some of them to scream in happiness at your return. It will calm down in time. When you come in the door, don't make a fuss. Walk past her and do your own thing until she is calm, then praise her and greet her when she is calm. Do not acknowledge her until she is calm. She will learn that her theatrics will not get attention from you, but if she is calm, she will get more pets.